MechWarrior Online (New) - Page 48

1. Use the local Champion 'mech. It'll be the trial 'mech with a (c ) after its name..
2. Stick with your team at all times, no matter what, unless you're leading 2:1 or more. And usually even then.
3. Try to always shoot at something other people are shooting at.
4. Generally, aim for center body mass. If you have FPS/Mechwarrior experience, try legging lights and zippy mediums.
5. http://mwo.smurfy-net.de/mechlab
6. Read other guides here and on the MWO forums!

This is a complicated question with complicated answers. Let's make it simple: get either a Catapult (CPLT) or a Hunchback (HBK). Both are useful, fun to level, and interesting in variants. Which of the two you want comes down to preference. I would generally recommend the HBK if you have MechWarrior experience and/or prefer to be up close in the enemy's face. I would recommend the CPLT more generally to most new players. The specific variant you should start with is the...

CPLT-C1
This is the finest starter 'mech in the game. It teaches many areas of the game, even though your basic mission profile is simple: stay 100-300m behind the center of your team and, whenever you have a red circle lock, firing missiles into the poor saps on the other team. Your range profile looks like this:
1000-300m: Missiles only
300-180m: Lasers and Missiles, prefer Missiles
180-0m: Lasers only
Your lasers are less heat efficient, but allow you to add damage in the 300-180m range overlap. Under 180m, your missiles are useless. Backpedal if you can to keep enemies in missile range as long as possible.

In time, you can upgrade your C1 to make it stronger. The order of upgrades you should get for the C1 in particular is more or less the list of upgrades you should get for all 'mechs in general:
0. Rip out the Jump Jets. You aren't ready yet.
1. Double Heat Sinks...crucial on all 'mechs. shoot for a smurfy heat efficiency over 40. http://mwo.smurfy-net.de/
2. Endo Steel Structure...crucial for all non-assault 'mechs, and many of those too
3. XL 300 Engine...most useful engine in the game, though there are some 'mechs that can't or shouldn't run it. See my 'mechlab guide for more.
4. Artemis FCS...increases LRM power if you can see the target. Can be a matter of personal preference. I use it.
5. Jump Jets...add 'em back in. Try em out. Make 'em work.

1. Always get faster engine than stock
2. Always max armor
-No exceptions for lights. But for mediums/heavies/assaults, only 3/4 or 1/2 armor on legs is ok
-Front/Back ratio should be 2:1 for scouts, 3:1 for most builds, and 4:1 for snipers
3. Always get Double Heat Sinks (DHS)
4. Usually get Endo Steel
5. Almost never get Ferro Fibrous, unless you have everything else you want and need more slots. It doesn't increase your armor cap, just slightly reduces your weight.
6. XL engines vary by 'mech. They are expensive, so get a 300XL and use it for everything that can fit it (swap it around, dont' sell it. only a handful of 'mechs can't take it.) With an XL, you die if you lose a side torso, but the XL is much lighter than the standard.

Good Mechs for an XL:
Any light: Commando, Jenner, Spider, Raven
Faster mediums: Cicada, Trebuchets
Big 'mechs with small side torsos: Catapult, Dragon
Bad Mechs for an XL:
Atlas, Awesome, Stalker (deceptively large side torsos)
Build Dependent Mechs:
Centurion:
SRM focused should get fast XL--note: cannot fit 300 except in CN9-D
AC/Laser focused should get fast Standard
Cataphract, Jagermech
Really better not to go XL, but some builds, like the 2xAC/20 Jager, require it for function.

Standard abreviations in MechWarrior/Battletech include:

H=Head (1 slot)
CT= Center Torso (2)
RT/LT= Right/Left Torso (12 standard, if XL engine, only 9)
CTR/RTR/LTR= Center/Right/Left Torso Rear (shares internals and slots with respective front section)
RL/LL= Right/Left Leg (2)
RA/LA= Right/Left Arm (slots complicated)

Slots in Arms:

10 Slots: Unarticulated Arms
Vertical Tracking only; cannot track horizontally beyond torso. Can mount more serious weaponry, such as dual UAC/5s or single AC/20s. 'Mechs with Unarticulated Arms are usually able to rotate their torsos farther than comparable 'mechs with Articulated Arms (including on the same chassis).
Mechs:
+ Show Spoiler +

9 Slots: Articulated Arms--No Hands
Horizontal and vertical tracking make for better aiming, particularly against faster targets. Tradeoff is less ability to mount some weapon setups.
Mechs:
+ Show Spoiler +

9/8 Slots: Articulated Arms--LA Hand only
Some 'mechs have a Left Hand but no Right. When melee is implemented, they will have a good LA punch to back up their RA weapons.
Mechs:
+ Show Spoiler +

8 Slots: Articulated Arms--With Hands
Currently, no advantage exists to 'mechs with hands. Eventually, hands will matter in the melee system, due to be part of the Solaris expansion, a year or so out from September release. Don't hold your breath.
Mechs:
+ Show Spoiler +

Loadout Implications of Articulation
Some examples of the kinda of loadouts that are restricted by certain arrangements of actuators. Note that several of these loadouts are possible on only a single 'mech chassis, due to hardpoint restrictions. Always use Smurfy to check out possible loadouts.

Loadouts Exclusive to Unarticulated (10 slot) Arms:
Note that XL 'mechs cannot run these loadouts in their side torsos
+ Show Spoiler +

Loadouts Only Possible for Handless (10 or 9 slot) Arms:
+ Show Spoiler +

All energy weapons in the game do max damage between 0 and [listed range] meters, then drop off linearly to do 0 damage at 2x[listed range].

All ballistic weapons are the same, but only drop off to 0 at 3x listed range (giving them better range per listed number, though they compensate with lower acuracy).

Missile weapons just blow up at listed max range, doing no damage. LRMs have a 180m arming range.

In MechWarrior, MechCommander, or the board game version, Battletech, critical hits are one of the most important systems to understand. It is also one of the most misunderstood. This is how the MWO version works.

See those "slots" in the 'mechlab? Every Arm and Torso segment has 12, and every Head and Leg has 6, no matter what the 'mech is (a Commando at 25 tons and an Atlas at 100 have the same number of slots).

Some of those are filled by "built-in" equipment like engines, gyros, the cockpit, various actuators (joints). As of right now, these cannot take critical damage. This may change later on. The "dynamic slots" added by Endo or Ferro (never get Ferro before Endo) cannot take critical hits, and never will. CASE ammo storage cannot take critical damage.

Everything else on your 'mech can take critical damage: heat sinks, weapons, electronics, ammunition.

Your 'mech is protected by armor plating and internal structure. On your 'mech doll in the HUD, internal structure is the filling, and the armor is the shell. Critical hits cannot currently go through armor, so a mech segment (a component) is safe from critical hits while armored.

However, when the armor is stripped off a component on your 'mech, the items inside become vulnerable. Luckily, most shots won't do any critical damage; they'll just hurt your internal structure and increase the chance of that component being destroyed. However, 42% of shots will do damage to both your internal structure and some items in the component. The amount of damage dealt is based on weapon damage, according to the below:
58% of the time, no critical damage.
25% chance 1x weapon damage, dealt to a random available critical slot in the component.
14% chance 2x weapon damage, dealt in packets like the above to 2 random available critical slots (can be the same one)
3% chance 3x weapon damage.

A few special weapons deal extra critical damage. Break these out against exposed internals. They are the Machine Gun, Flamer, and LB 10-X AC. Be aware that the MG and Flamer are underpowered due to being essentially only good at this. Debate exists on the LBX (shotgun autocannon).
Special critical values
33% 0 crits
33% 1 crit
28% 2 crits
6% 3 crits

Most items have 10 HP, and will be destroyed upon accumulating 10 damage. Gauss Rifles and ECMs are particularly fragile. AC/20s are particularly durable... but this is offset by their large slot count, meaning they are likely to take crit hits.

Destroyed items do not work, and ammo bins have a 10% chance of detonation on being destroyed, leading to a happy pop-pop-pop that will shell the poor 'mech unless the explosion is vented by a CASE system. CASE will not protect the side torso it is in, but will prevent the damage from going on to kill the center torso. Damage will naturally progress toward the center of a 'mech, from Arm or Leg to Side Torso to Center Torso. Passing each barrier reduces damage by 50%.

Gauss Rifles also have a 90% chance of detonation, and do 20 damage. Gauss Rifle ammo itself is inert. When a component with a Gauss Rifle or Ammo Bin are destroyed (regularly, not critical damage) they still have the same chance to go up in smoke. Crits just make it happen earlier.

Implications of Critical Hit System
Scoring Critical Hits
Your best bet to score good critical hits is just to hammer weakened body parts. Anything packing a Gauss Rifle is a juicy target. LBXs are good at this, but so are any weapon with a high enough damage value that a single crit will destroy a component. These include PPCs, AC10s, Gauss Rifles, and AC/20s.

Defending against Critical Hits
Don't get shot. Also, "crit pad."

Crit Padding is when you make use of the "damage is dealt to a random hittable location" mechanic. If you have a Gauss Rifle as the only thing in a component, when the component takes a single AC/10 hit, you have a 38% chance of having a real bad day. If, however, you throw in a Double Heat sink and 2 tons of Gauss Ammo, you have a little more than half that chance. Whenever you have something explosive in a segment, try not to leave any empty slots there. And if you use Gauss, you really should use CASE.

All ACs have about 150 damage per ton of ammo. This means a single AC type for the 'mech will need 3-5 tons. If you have 2 types of AC, each needs 1-3 tons.

The below listed by increasing weight

AC/2:
+Long range,
+Excellent DPS per tonnage
+Rocks the enemy like a wagonwheel
+High projectile speed
-Terrible heat/damage ratio (for a ballistic... similar to missiles but still better than lasers)
-Damage scattered all over target
-Need lots of ammo due to damage inefficency

AC/5:
+Can be useful due to lowish weight and ability to aim shots
+Most heat efficient AC, so good if tight on heat and spare on tons
~Only useful if extremely skilled and using as direct fire support (high RoF sniper)
-Low DPS
-Sucks


UAC/5:
+Absurd DPS
+Best noise in game
~Generally similar pros and cons to AC/2. Pairs well with it.
-Biggest ammo-hog in game
-Jams make firepower unreliable. Best used if cover available to hid during jams. But boated, can just stand ground and press trigger.

LB10-X AC:
+Scattershot
+Good if you can't hit things
++Bonus to crit damage
+Lightish for job
-Scattershot
-Limited range
-Low striking power, DPS

AC/10:
+Biggest AC that can fit on arms with lower actuators (elbows, which allow horizontal arm articulation)
+Most versitile weapon in game except ML, with which it pairs nicely
+Style points
~Basically a bigger AC/5. Shorter range, more concentrated damage
-Generally better to trade up to AC/20, though you lose range
-Lowish DPS

AC20:
+20 f*ckin' points of m*therf*ckin' damage per hit
+2 head hits drops any 'mech in game (pairing these on a Jagermech or Cat K2 is often a good idea). Means auto-kill on Catapults that let you get to close range if you can nail your shots.
+High damage and low RoF great for popping in and out of cover
+Efficient kills mean you KS a lot, and use relatively little ammo. (Flipside: can't use damage score for E-Peening)
-Really easy to lose to critical hits
-Low projectile velocity and RoF means you have to be on top of your shots
-Really heavy
-Can't mount in a torso if have XL engine
-Can't mount in the arm of a 'mech with lower arm actuators (see note for AC/10).

Mechs that can mount an AC/20 in their arms:
Highlander 733C
Jagermech (all can mount 1 in each arm... result of using both is the dreaded "Jagerbomb")
Centurion YLW (Hero variant)
Raven 4X

Any 'mech with a ballistic hardpoint in the torso can mount an AC/20, but many are ill advised to use XL engines.

All of this said, try different weapons out and see what works for you. I love AC/10s, despite them being the 2nd weakest AC. My lancemate is even crazier: he uses a 4 AC/5 Cataphract 4X. Does amazing with it. Really nails his shots, because the AC/5 cooldown gives him a moment to line each up and fire with clicks rather than mashing. Each volley hits like an AC/20, and can reach out really far. But it's a very difficult build to pull off unless you really have a lot of faith in your ability to keep hitting the legs of jumping 'mechs at 1000m.

Oh, and remember that each ballistic still does damage out to almost 3x its max listed range! (Linearly less from it though.)

Unlike ACs, Laser weapons get more powerful as they get longer-range, though efficiency suffers. Important things to keep track of are DPS/ton and Damage/heat, which show efficiency in 'mechlab and when under high-heat conditions on the field. Energy weapons generally have superior DPS/ton to ballistics, but substantially worse damage/heat. NB: PPC line and flamers not in this Laser guide. They will appear later with their actual peers, respectively the Gauss (Sniper Weapons) and Flamer (Crit-Seekers).

The below listed by increasing weight and heat

Small Laser
+Insane DPS/ton
+Insane damage/heat for an energy weapon
+Weighs .5 tons, good for filling out load-outs
-Weak individually, which means hardpoints prevent too much boating of these
-Hardpoints mean these work better on smaller mechs (which have more HP/tons)
---Piss-poor range. Like really, really bad.

Small Pulse Laser
+Shortest burn time of lasers with hitscan means great accuracy for ankle-biters who want to take a shot and turn away
-Objectively the worst weapon in the game. Recently buffed, so not wholly inferior to the ML, but we'll have to see how it fares in the meta.

Medium Laser
+Most versatile weapon in game. Good combination of traits. I run it on essentially all of my builds as the standard back-up weapon. Hard to boat as a primary due to hardpoints, but great as a secondary. Some variants can boat for high heat but great short range power.
+Great DPS/ton
+Easy to hit lights
+Weighs 1 ton, 1 slot
-Fairly short range
-Hard to boat
-Heat gets up there in larger numbers

Medium Pulse Laser
+Slightly better heat/damage than ML
+Better at fitting into limited hardpoints (e.g. CT energy slots on CN9) than ML
+Faster burn time makes it really good for concentrating damage on scouts
-Substantially worse DPS/ton than ML
-Lower range than ML
-Inferior to ML except for specialty applications

Large Laser
+LL line is only way to get laser mechanic (easy to hit) with significant damage per hardpoint, making them popular with heavies and assaults
+Good range for a laser
-Way heavier than other laser models (at 5 tons 10x the SL, 5x the ML)
-Lacks the great efficiency that characterizes other lasers

Extended Range Large Laser (ERLL)
+Popular as a pinch sniper. Tonnage cheap way to get long range damage
-On paper and by stats, a terrible weapon. The efficiency you want from a laser is not here

Large Pulse Laser
+High damage with short burn and hitscan. Good for assault 'mechs looking for scout-hunting capability
-Really bad efficiency

Of course, use this only as an outline. Try out what weapons work for you. Stats aren't everything, as the popularity of the LL line shows. MPLs in particular have their fans, despite being kinda sub-optimal by the numbers.

Oh, and remember that each energy weapon still does damage out to almost 2x its max listed range! (Linearly less from it though, which decreases heat efficiency)

The favored weapons of the current meta, Sniper weapons make huge sacrifices in efficiency and stats for range, and high damage per strike at that range.

The below listed by increasing weight and heat

Suppression Weapons
AC/2
+A capable long range weapon with unusually good brawling capability
+Projectile speed and RoF give it a unique role as a targeting weapon: if you're leading right to hit with the AC/2, you'll land your PPC and GR shots.
+High DPS. In a long-range stand-and-fight scenario, the best weapon out there.
-Tiny damage packets mean that it is unsuited to Sniper work. Cannot duck in and out of cover, and damage tends to scatter across the target.

Large Laser and ER LL
+Longest range hitscan weapons. With burn time, makes them very accurate.
+Excellent for precision work, such as focusing down a weakened side torso, or attempting a headshot
+Great for anti-scout work at close range, for a long range weapon. Great at "sweeping the leg"
-Scattered damage
-Shorter range than the other weapons on this list

True Sniper Weapons
PPC
+Most generally useful sniper weapon, most favored weapon in current meta
+Especially when fired in groups, crazy damage per burst
+Heat limitation is mitigated if you can duck behind cover after each shot
+Remarkably fast cycle time allows serious DPS as heat allows
+Kills ECM for 3 seconds, allowing complete suppression of ECM with a single PPC and good enough shooting
-High heat, limiting usefulness in a brawl (where it's hard to find cover)
-Minimum range (damage falls of linearly from 10 at 90m to 0 at 0m) further limits usefulness in a brawl
-Draws a lot of attention fast. Flankers look for places emanating LRMs or PPC bolts as easy prey
-Large, high-heat energy weapon with projectile attack. This means that it doesn't pair great with MLs, the standard backup weapon. The synergy forces you into either SLs, MLs fired sparingly, SRMs, or SSRMs (with BAP if you don't have the heat to use PPCs to keep ECM negated)
-Boating requires insane amounts of DHS, and usually a big engine to help out. This often forces PPC boats into larger standard engines, which are really heavy

ER-PPC
+All listed for PPC
+NO MINIMUM RANGE. If you've got a good eye, you can drop scouts and flankers easily with the ER-PPC.
+Superior maximum range to PPC, among the longest in game
+No additional slots or tonnage compared to PPC
-Highest heat in game per shot, and bad efficiency to boot
-Heat exacerbates the biggest limitation of the PPC

Gauss
+Almost no heat at all
+Synergizes great with PPC or ML, for more sniper power or more backup flexibility
+Second highest damage per shot in game
+Ammo does not explode
+Does significant damage past a kilometer, and only drops off to 0 at around 2km. If you can hit it, you'll do good damage
-Ammo dependent
-Heaviest weapon in the game (mitigated by lack of heat requirements)
-Lot of slots
-Low hitpoints make it vulnerable to destruction
-Explodes for 15 damage 90% of the time on component or item destruction. In an XL 'mech or anything small, this has a decent chance of killing you outright
-Brawl with it, and prepare for a humiliating self-inflicted death

As usual, experiment to find your favorites!

Oh, and remember that each energy weapon still does damage out to almost 2x its max listed range! (Linearly less from it though, which decreases heat efficiency)

Ballistics drop off linearly to 3x effective range (the listed one). This is a notable advantage

Since it matters, here is a list of range data on long range weapons:
AC/2: ..…720……2,160
Gauss: …660……1,980 (better damage percentage than ER-PPC outside of around 1,250)
ER PPC:.810…….1,620
PPC:……540……1,080

With Centurions, you really get to pick from 2 options:

1) AC-based
Right arm cannon, backed up by CT lasers and streaks (the latter to fend off scouts). Uncommonly feature LRMs, but this is sub-optimal.

2) SRM-based
No cannon, but using multiple large SRM-packs. 3x6 is possible. Occasionally uses XL engine, particularly in CN9-D variant.

Be aware that these go for the A, D, and YLW variants. The AL is a different beast and can be set up as a scout hunter (lasers and streaks) or pinch sniper (2xPPCs in RA).

Never use a CN9 with a <250 engine rating. Max engine rating is preferable.

ZOMBIE CENTURIONS:
Cn9s can be really good "zombie 'mechs." This means they can limp around the battlefield on one leg, both side torsos and attached arms destroyed, and still put out respectable damage after the enemy has decided you aren't worth focusing on. This is because of (1) good hitboxes that soak damage and (2) all variants can pack 2 ML or MPL in the center torso, giving you moderate DPS way after you should be dead. The best zombie is actually the hero CN9-YLW, because it has superior torso twist to compensate for now having elbows. Mechs with XL engines obviously cannot zombie.

1. Use the local Champion 'mech. It'll be the trial 'mech with a (c ) after its name..
2. Stick with your team at all times, no matter what, unless you're leading 2:1 or more. And usually even then.
3. Try to always shoot at something other people are shooting at.
4. Generally, aim for center body mass. If you have FPS/Mechwarrior experience, try legging lights and zippy mediums.
5. http://mwo.smurfy-net.de/mechlab
6. Read other guides here and on the MWO forums!

This is a complicated question with complicated answers. Let's make it simple: get either a Catapult (CPLT) or a Hunchback (HBK). Both are useful, fun to level, and interesting in variants. Which of the two you want comes down to preference. I would generally recommend the HBK if you have MechWarrior experience and/or prefer to be up close in the enemy's face. I would recommend the CPLT more generally to most new players. The specific variant you should start with is the...

CPLT-C1
This is the finest starter 'mech in the game. It teaches many areas of the game, even though your basic mission profile is simple: stay 100-300m behind the center of your team and, whenever you have a red circle lock, firing missiles into the poor saps on the other team. Your range profile looks like this:
1000-300m: Missiles only
300-180m: Lasers and Missiles, prefer Missiles
180-0m: Lasers only
Your lasers are less heat efficient, but allow you to add damage in the 300-180m range overlap. Under 180m, your missiles are useless. Backpedal if you can to keep enemies in missile range as long as possible.

In time, you can upgrade your C1 to make it stronger. The order of upgrades you should get for the C1 in particular is more or less the list of upgrades you should get for all 'mechs in general:
0. Rip out the Jump Jets. You aren't ready yet.
1. Double Heat Sinks...crucial on all 'mechs. shoot for a smurfy heat efficiency over 40. http://mwo.smurfy-net.de/
2. Endo Steel Structure...crucial for all non-assault 'mechs, and many of those too
3. XL 300 Engine...most useful engine in the game, though there are some 'mechs that can't or shouldn't run it. See my 'mechlab guide for more.
4. Artemis FCS...increases LRM power if you can see the target. Can be a matter of personal preference. I use it.
5. Jump Jets...add 'em back in. Try em out. Make 'em work.

1. Always get faster engine than stock
2. Always max armor
-No exceptions for lights. But for mediums/heavies/assaults, only 3/4 or 1/2 armor on legs is ok
-Front/Back ratio should be 2:1 for scouts, 3:1 for most builds, and 4:1 for snipers
3. Always get Double Heat Sinks (DHS)
4. Usually get Endo Steel
5. Almost never get Ferro Fibrous, unless you have everything else you want and need more slots. It doesn't increase your armor cap, just slightly reduces your weight.
6. XL engines vary by 'mech. They are expensive, so get a 300XL and use it for everything that can fit it (swap it around, dont' sell it. only a handful of 'mechs can't take it.) With an XL, you die if you lose a side torso, but the XL is much lighter than the standard.

Good Mechs for an XL:
Any light: Commando, Jenner, Spider, Raven
Faster mediums: Cicada, Trebuchets
Big 'mechs with small side torsos: Catapult, Dragon
Bad Mechs for an XL:
Atlas, Awesome, Stalker (deceptively large side torsos)
Build Dependent Mechs:
Centurion:
SRM focused should get fast XL--note: cannot fit 300 except in CN9-D
AC/Laser focused should get fast Standard
Cataphract, Jagermech
Really better not to go XL, but some builds, like the 2xAC/20 Jager, require it for function.

Standard abreviations in MechWarrior/Battletech include:

H=Head (1 slot)
CT= Center Torso (2)
RT/LT= Right/Left Torso (12 standard, if XL engine, only 9)
CTR/RTR/LTR= Center/Right/Left Torso Rear (shares internals and slots with respective front section)
RL/LL= Right/Left Leg (2)
RA/LA= Right/Left Arm (slots complicated)

Slots in Arms:

10 Slots: Unarticulated Arms
Vertical Tracking only; cannot track horizontally beyond torso. Can mount more serious weaponry, such as dual UAC/5s or single AC/20s. 'Mechs with Unarticulated Arms are usually able to rotate their torsos farther than comparable 'mechs with Articulated Arms (including on the same chassis).
Mechs:
+ Show Spoiler +

9 Slots: Articulated Arms--No Hands
Horizontal and vertical tracking make for better aiming, particularly against faster targets. Tradeoff is less ability to mount some weapon setups.
Mechs:
+ Show Spoiler +

9/8 Slots: Articulated Arms--LA Hand only
Some 'mechs have a Left Hand but no Right. When melee is implemented, they will have a good LA punch to back up their RA weapons.
Mechs:
+ Show Spoiler +

8 Slots: Articulated Arms--With Hands
Currently, no advantage exists to 'mechs with hands. Eventually, hands will matter in the melee system, due to be part of the Solaris expansion, a year or so out from September release. Don't hold your breath.
Mechs:
+ Show Spoiler +

Loadout Implications of Articulation
Some examples of the kinda of loadouts that are restricted by certain arrangements of actuators. Note that several of these loadouts are possible on only a single 'mech chassis, due to hardpoint restrictions. Always use Smurfy to check out possible loadouts.

Loadouts Exclusive to Unarticulated (10 slot) Arms:
Note that XL 'mechs cannot run these loadouts in their side torsos
+ Show Spoiler +

Loadouts Only Possible for Handless (10 or 9 slot) Arms:
+ Show Spoiler +

All energy weapons in the game do max damage between 0 and [listed range] meters, then drop off linearly to do 0 damage at 2x[listed range].

All ballistic weapons are the same, but only drop off to 0 at 3x listed range (giving them better range per listed number, though they compensate with lower acuracy).

Missile weapons just blow up at listed max range, doing no damage. LRMs have a 180m arming range.

In MechWarrior, MechCommander, or the board game version, Battletech, critical hits are one of the most important systems to understand. It is also one of the most misunderstood. This is how the MWO version works.

See those "slots" in the 'mechlab? Every Arm and Torso segment has 12, and every Head and Leg has 6, no matter what the 'mech is (a Commando at 25 tons and an Atlas at 100 have the same number of slots).

Some of those are filled by "built-in" equipment like engines, gyros, the cockpit, various actuators (joints). As of right now, these cannot take critical damage. This may change later on. The "dynamic slots" added by Endo or Ferro (never get Ferro before Endo) cannot take critical hits, and never will. CASE ammo storage cannot take critical damage.

Everything else on your 'mech can take critical damage: heat sinks, weapons, electronics, ammunition.

Your 'mech is protected by armor plating and internal structure. On your 'mech doll in the HUD, internal structure is the filling, and the armor is the shell. Critical hits cannot currently go through armor, so a mech segment (a component) is safe from critical hits while armored.

However, when the armor is stripped off a component on your 'mech, the items inside become vulnerable. Luckily, most shots won't do any critical damage; they'll just hurt your internal structure and increase the chance of that component being destroyed. However, 42% of shots will do damage to both your internal structure and some items in the component. The amount of damage dealt is based on weapon damage, according to the below:
58% of the time, no critical damage.
25% chance 1x weapon damage, dealt to a random available critical slot in the component.
14% chance 2x weapon damage, dealt in packets like the above to 2 random available critical slots (can be the same one)
3% chance 3x weapon damage.

A few special weapons deal extra critical damage. Break these out against exposed internals. They are the Machine Gun, Flamer, and LB 10-X AC. Be aware that the MG and Flamer are underpowered due to being essentially only good at this. Debate exists on the LBX (shotgun autocannon).
Special critical values
33% 0 crits
33% 1 crit
28% 2 crits
6% 3 crits

Most items have 10 HP, and will be destroyed upon accumulating 10 damage. Gauss Rifles and ECMs are particularly fragile. AC/20s are particularly durable... but this is offset by their large slot count, meaning they are likely to take crit hits.

Destroyed items do not work, and ammo bins have a 10% chance of detonation on being destroyed, leading to a happy pop-pop-pop that will shell the poor 'mech unless the explosion is vented by a CASE system. CASE will not protect the side torso it is in, but will prevent the damage from going on to kill the center torso. Damage will naturally progress toward the center of a 'mech, from Arm or Leg to Side Torso to Center Torso. Passing each barrier reduces damage by 50%.

Gauss Rifles also have a 90% chance of detonation, and do 20 damage. Gauss Rifle ammo itself is inert. When a component with a Gauss Rifle or Ammo Bin are destroyed (regularly, not critical damage) they still have the same chance to go up in smoke. Crits just make it happen earlier.

Implications of Critical Hit System
Scoring Critical Hits
Your best bet to score good critical hits is just to hammer weakened body parts. Anything packing a Gauss Rifle is a juicy target. LBXs are good at this, but so are any weapon with a high enough damage value that a single crit will destroy a component. These include PPCs, AC10s, Gauss Rifles, and AC/20s.

Defending against Critical Hits
Don't get shot. Also, "crit pad."

Crit Padding is when you make use of the "damage is dealt to a random hittable location" mechanic. If you have a Gauss Rifle as the only thing in a component, when the component takes a single AC/10 hit, you have a 38% chance of having a real bad day. If, however, you throw in a Double Heat sink and 2 tons of Gauss Ammo, you have a little more than half that chance. Whenever you have something explosive in a segment, try not to leave any empty slots there. And if you use Gauss, you really should use CASE.

All ACs have about 150 damage per ton of ammo. This means a single AC type for the 'mech will need 3-5 tons. If you have 2 types of AC, each needs 1-3 tons.

The below listed by increasing weight

AC/2:
+Long range,
+Excellent DPS per tonnage
+Rocks the enemy like a wagonwheel
+High projectile speed
-Terrible heat/damage ratio (for a ballistic... similar to missiles but still better than lasers)
-Damage scattered all over target
-Need lots of ammo due to damage inefficency

AC/5:
+Can be useful due to lowish weight and ability to aim shots
+Most heat efficient AC, so good if tight on heat and spare on tons
~Only useful if extremely skilled and using as direct fire support (high RoF sniper)
-Low DPS
-Sucks


UAC/5:
+Absurd DPS
+Best noise in game
~Generally similar pros and cons to AC/2. Pairs well with it.
-Biggest ammo-hog in game
-Jams make firepower unreliable. Best used if cover available to hid during jams. But boated, can just stand ground and press trigger.

LB10-X AC:
+Scattershot
+Good if you can't hit things
++Bonus to crit damage
+Lightish for job
-Scattershot
-Limited range
-Low striking power, DPS

AC/10:
+Biggest AC that can fit on arms with lower actuators (elbows, which allow horizontal arm articulation)
+Most versitile weapon in game except ML, with which it pairs nicely
+Style points
~Basically a bigger AC/5. Shorter range, more concentrated damage
-Generally better to trade up to AC/20, though you lose range
-Lowish DPS

AC20:
+20 f*ckin' points of m*therf*ckin' damage per hit
+2 head hits drops any 'mech in game (pairing these on a Jagermech or Cat K2 is often a good idea). Means auto-kill on Catapults that let you get to close range if you can nail your shots.
+High damage and low RoF great for popping in and out of cover
+Efficient kills mean you KS a lot, and use relatively little ammo. (Flipside: can't use damage score for E-Peening)
-Really easy to lose to critical hits
-Low projectile velocity and RoF means you have to be on top of your shots
-Really heavy
-Can't mount in a torso if have XL engine
-Can't mount in the arm of a 'mech with lower arm actuators (see note for AC/10).

Mechs that can mount an AC/20 in their arms:
Highlander 733C
Jagermech (all can mount 1 in each arm... result of using both is the dreaded "Jagerbomb")
Centurion YLW (Hero variant)
Raven 4X

Any 'mech with a ballistic hardpoint in the torso can mount an AC/20, but many are ill advised to use XL engines.

All of this said, try different weapons out and see what works for you. I love AC/10s, despite them being the 2nd weakest AC. My lancemate is even crazier: he uses a 4 AC/5 Cataphract 4X. Does amazing with it. Really nails his shots, because the AC/5 cooldown gives him a moment to line each up and fire with clicks rather than mashing. Each volley hits like an AC/20, and can reach out really far. But it's a very difficult build to pull off unless you really have a lot of faith in your ability to keep hitting the legs of jumping 'mechs at 1000m.

Oh, and remember that each ballistic still does damage out to almost 3x its max listed range! (Linearly less from it though.)

Unlike ACs, Laser weapons get more powerful as they get longer-range, though efficiency suffers. Important things to keep track of are DPS/ton and Damage/heat, which show efficiency in 'mechlab and when under high-heat conditions on the field. Energy weapons generally have superior DPS/ton to ballistics, but substantially worse damage/heat. NB: PPC line and flamers not in this Laser guide. They will appear later with their actual peers, respectively the Gauss (Sniper Weapons) and Flamer (Crit-Seekers).

The below listed by increasing weight and heat

Small Laser
+Insane DPS/ton
+Insane damage/heat for an energy weapon
+Weighs .5 tons, good for filling out load-outs
-Weak individually, which means hardpoints prevent too much boating of these
-Hardpoints mean these work better on smaller mechs (which have more HP/tons)
---Piss-poor range. Like really, really bad.

Small Pulse Laser
+Shortest burn time of lasers with hitscan means great accuracy for ankle-biters who want to take a shot and turn away
-Objectively the worst weapon in the game. Recently buffed, so not wholly inferior to the ML, but we'll have to see how it fares in the meta.

Medium Laser
+Most versatile weapon in game. Good combination of traits. I run it on essentially all of my builds as the standard back-up weapon. Hard to boat as a primary due to hardpoints, but great as a secondary. Some variants can boat for high heat but great short range power.
+Great DPS/ton
+Easy to hit lights
+Weighs 1 ton, 1 slot
-Fairly short range
-Hard to boat
-Heat gets up there in larger numbers

Medium Pulse Laser
+Slightly better heat/damage than ML
+Better at fitting into limited hardpoints (e.g. CT energy slots on CN9) than ML
+Faster burn time makes it really good for concentrating damage on scouts
-Substantially worse DPS/ton than ML
-Lower range than ML
-Inferior to ML except for specialty applications

Large Laser
+LL line is only way to get laser mechanic (easy to hit) with significant damage per hardpoint, making them popular with heavies and assaults
+Good range for a laser
-Way heavier than other laser models (at 5 tons 10x the SL, 5x the ML)
-Lacks the great efficiency that characterizes other lasers

Extended Range Large Laser (ERLL)
+Popular as a pinch sniper. Tonnage cheap way to get long range damage
-On paper and by stats, a terrible weapon. The efficiency you want from a laser is not here

Large Pulse Laser
+High damage with short burn and hitscan. Good for assault 'mechs looking for scout-hunting capability
-Really bad efficiency

Of course, use this only as an outline. Try out what weapons work for you. Stats aren't everything, as the popularity of the LL line shows. MPLs in particular have their fans, despite being kinda sub-optimal by the numbers.

Oh, and remember that each energy weapon still does damage out to almost 2x its max listed range! (Linearly less from it though, which decreases heat efficiency)

The favored weapons of the current meta, Sniper weapons make huge sacrifices in efficiency and stats for range, and high damage per strike at that range.

The below listed by increasing weight and heat

Suppression Weapons
AC/2
+A capable long range weapon with unusually good brawling capability
+Projectile speed and RoF give it a unique role as a targeting weapon: if you're leading right to hit with the AC/2, you'll land your PPC and GR shots.
+High DPS. In a long-range stand-and-fight scenario, the best weapon out there.
-Tiny damage packets mean that it is unsuited to Sniper work. Cannot duck in and out of cover, and damage tends to scatter across the target.

Large Laser and ER LL
+Longest range hitscan weapons. With burn time, makes them very accurate.
+Excellent for precision work, such as focusing down a weakened side torso, or attempting a headshot
+Great for anti-scout work at close range, for a long range weapon. Great at "sweeping the leg"
-Scattered damage
-Shorter range than the other weapons on this list

True Sniper Weapons
PPC
+Most generally useful sniper weapon, most favored weapon in current meta
+Especially when fired in groups, crazy damage per burst
+Heat limitation is mitigated if you can duck behind cover after each shot
+Remarkably fast cycle time allows serious DPS as heat allows
+Kills ECM for 3 seconds, allowing complete suppression of ECM with a single PPC and good enough shooting
-High heat, limiting usefulness in a brawl (where it's hard to find cover)
-Minimum range (damage falls of linearly from 10 at 90m to 0 at 0m) further limits usefulness in a brawl
-Draws a lot of attention fast. Flankers look for places emanating LRMs or PPC bolts as easy prey
-Large, high-heat energy weapon with projectile attack. This means that it doesn't pair great with MLs, the standard backup weapon. The synergy forces you into either SLs, MLs fired sparingly, SRMs, or SSRMs (with BAP if you don't have the heat to use PPCs to keep ECM negated)
-Boating requires insane amounts of DHS, and usually a big engine to help out. This often forces PPC boats into larger standard engines, which are really heavy

ER-PPC
+All listed for PPC
+NO MINIMUM RANGE. If you've got a good eye, you can drop scouts and flankers easily with the ER-PPC.
+Superior maximum range to PPC, among the longest in game
+No additional slots or tonnage compared to PPC
-Highest heat in game per shot, and bad efficiency to boot
-Heat exacerbates the biggest limitation of the PPC

Gauss
+Almost no heat at all
+Synergizes great with PPC or ML, for more sniper power or more backup flexibility
+Second highest damage per shot in game
+Ammo does not explode
+Does significant damage past a kilometer, and only drops off to 0 at around 2km. If you can hit it, you'll do good damage
-Ammo dependent
-Heaviest weapon in the game (mitigated by lack of heat requirements)
-Lot of slots
-Low hitpoints make it vulnerable to destruction
-Explodes for 15 damage 90% of the time on component or item destruction. In an XL 'mech or anything small, this has a decent chance of killing you outright
-Brawl with it, and prepare for a humiliating self-inflicted death

As usual, experiment to find your favorites!

Oh, and remember that each energy weapon still does damage out to almost 2x its max listed range! (Linearly less from it though, which decreases heat efficiency)

Ballistics drop off linearly to 3x effective range (the listed one). This is a notable advantage

Since it matters, here is a list of range data on long range weapons:
AC/2: ..…720……2,160
Gauss: …660……1,980 (better damage percentage than ER-PPC outside of around 1,250)
ER PPC:.810…….1,620
PPC:……540……1,080

With Centurions, you really get to pick from 2 options:

1) AC-based
Right arm cannon, backed up by CT lasers and streaks (the latter to fend off scouts). Uncommonly feature LRMs, but this is sub-optimal.

2) SRM-based
No cannon, but using multiple large SRM-packs. 3x6 is possible. Occasionally uses XL engine, particularly in CN9-D variant.

Be aware that these go for the A, D, and YLW variants. The AL is a different beast and can be set up as a scout hunter (lasers and streaks) or pinch sniper (2xPPCs in RA).

Never use a CN9 with a <250 engine rating. Max engine rating is preferable.

ZOMBIE CENTURIONS:
Cn9s can be really good "zombie 'mechs." This means they can limp around the battlefield on one leg, both side torsos and attached arms destroyed, and still put out respectable damage after the enemy has decided you aren't worth focusing on. This is because of (1) good hitboxes that soak damage and (2) all variants can pack 2 ML or MPL in the center torso, giving you moderate DPS way after you should be dead. The best zombie is actually the hero CN9-YLW, because it has superior torso twist to compensate for now having elbows. Mechs with XL engines obviously cannot zombie.

1. Use the local Champion 'mech. It'll be the trial 'mech with a (c ) after its name..
2. Stick with your team at all times, no matter what, unless you're leading 2:1 or more. And usually even then.
3. Try to always shoot at something other people are shooting at.
4. Generally, aim for center body mass. If you have FPS/Mechwarrior experience, try legging lights and zippy mediums.
5. http://mwo.smurfy-net.de/mechlab
6. Read other guides here and on the MWO forums!

This is a complicated question with complicated answers. Let's make it simple: get either a Catapult (CPLT) or a Hunchback (HBK). Both are useful, fun to level, and interesting in variants. Which of the two you want comes down to preference. I would generally recommend the HBK if you have MechWarrior experience and/or prefer to be up close in the enemy's face. I would recommend the CPLT more generally to most new players. The specific variant you should start with is the...

CPLT-C1
This is the finest starter 'mech in the game. It teaches many areas of the game, even though your basic mission profile is simple: stay 100-300m behind the center of your team and, whenever you have a red circle lock, firing missiles into the poor saps on the other team. Your range profile looks like this:
1000-300m: Missiles only
300-180m: Lasers and Missiles, prefer Missiles
180-0m: Lasers only
Your lasers are less heat efficient, but allow you to add damage in the 300-180m range overlap. Under 180m, your missiles are useless. Backpedal if you can to keep enemies in missile range as long as possible.

In time, you can upgrade your C1 to make it stronger. The order of upgrades you should get for the C1 in particular is more or less the list of upgrades you should get for all 'mechs in general:
0. Rip out the Jump Jets. You aren't ready yet.
1. Double Heat Sinks...crucial on all 'mechs. shoot for a smurfy heat efficiency over 40. http://mwo.smurfy-net.de/
2. Endo Steel Structure...crucial for all non-assault 'mechs, and many of those too
3. XL 300 Engine...most useful engine in the game, though there are some 'mechs that can't or shouldn't run it. See my 'mechlab guide for more.
4. Artemis FCS...increases LRM power if you can see the target. Can be a matter of personal preference. I use it.
5. Jump Jets...add 'em back in. Try em out. Make 'em work.

1. Always get faster engine than stock
2. Always max armor
-No exceptions for lights. But for mediums/heavies/assaults, only 3/4 or 1/2 armor on legs is ok
-Front/Back ratio should be 2:1 for scouts, 3:1 for most builds, and 4:1 for snipers
3. Always get Double Heat Sinks (DHS)
4. Usually get Endo Steel
5. Almost never get Ferro Fibrous, unless you have everything else you want and need more slots. It doesn't increase your armor cap, just slightly reduces your weight.
6. XL engines vary by 'mech. They are expensive, so get a 300XL and use it for everything that can fit it (swap it around, dont' sell it. only a handful of 'mechs can't take it.) With an XL, you die if you lose a side torso, but the XL is much lighter than the standard.

Good Mechs for an XL:
Any light: Commando, Jenner, Spider, Raven
Faster mediums: Cicada, Trebuchets
Big 'mechs with small side torsos: Catapult, Dragon
Bad Mechs for an XL:
Atlas, Awesome, Stalker (deceptively large side torsos)
Build Dependent Mechs:
Centurion:
SRM focused should get fast XL--note: cannot fit 300 except in CN9-D
AC/Laser focused should get fast Standard
Cataphract, Jagermech
Really better not to go XL, but some builds, like the 2xAC/20 Jager, require it for function.

Standard abreviations in MechWarrior/Battletech include:

H=Head (1 slot)
CT= Center Torso (2)
RT/LT= Right/Left Torso (12 standard, if XL engine, only 9)
CTR/RTR/LTR= Center/Right/Left Torso Rear (shares internals and slots with respective front section)
RL/LL= Right/Left Leg (2)
RA/LA= Right/Left Arm (slots complicated)

Slots in Arms:

10 Slots: Unarticulated Arms
Vertical Tracking only; cannot track horizontally beyond torso. Can mount more serious weaponry, such as dual UAC/5s or single AC/20s. 'Mechs with Unarticulated Arms are usually able to rotate their torsos farther than comparable 'mechs with Articulated Arms (including on the same chassis).
Mechs:
+ Show Spoiler +

9 Slots: Articulated Arms--No Hands
Horizontal and vertical tracking make for better aiming, particularly against faster targets. Tradeoff is less ability to mount some weapon setups.
Mechs:
+ Show Spoiler +

9/8 Slots: Articulated Arms--LA Hand only
Some 'mechs have a Left Hand but no Right. When melee is implemented, they will have a good LA punch to back up their RA weapons.
Mechs:
+ Show Spoiler +

8 Slots: Articulated Arms--With Hands
Currently, no advantage exists to 'mechs with hands. Eventually, hands will matter in the melee system, due to be part of the Solaris expansion, a year or so out from September release. Don't hold your breath.
Mechs:
+ Show Spoiler +

Loadout Implications of Articulation
Some examples of the kinda of loadouts that are restricted by certain arrangements of actuators. Note that several of these loadouts are possible on only a single 'mech chassis, due to hardpoint restrictions. Always use Smurfy to check out possible loadouts.

Loadouts Exclusive to Unarticulated (10 slot) Arms:
Note that XL 'mechs cannot run these loadouts in their side torsos
+ Show Spoiler +

Loadouts Only Possible for Handless (10 or 9 slot) Arms:
+ Show Spoiler +

All energy weapons in the game do max damage between 0 and [listed range] meters, then drop off linearly to do 0 damage at 2x[listed range].

All ballistic weapons are the same, but only drop off to 0 at 3x listed range (giving them better range per listed number, though they compensate with lower acuracy).

Missile weapons just blow up at listed max range, doing no damage. LRMs have a 180m arming range.

In MechWarrior, MechCommander, or the board game version, Battletech, critical hits are one of the most important systems to understand. It is also one of the most misunderstood. This is how the MWO version works.

See those "slots" in the 'mechlab? Every Arm and Torso segment has 12, and every Head and Leg has 6, no matter what the 'mech is (a Commando at 25 tons and an Atlas at 100 have the same number of slots).

Some of those are filled by "built-in" equipment like engines, gyros, the cockpit, various actuators (joints). As of right now, these cannot take critical damage. This may change later on. The "dynamic slots" added by Endo or Ferro (never get Ferro before Endo) cannot take critical hits, and never will. CASE ammo storage cannot take critical damage.

Everything else on your 'mech can take critical damage: heat sinks, weapons, electronics, ammunition.

Your 'mech is protected by armor plating and internal structure. On your 'mech doll in the HUD, internal structure is the filling, and the armor is the shell. Critical hits cannot currently go through armor, so a mech segment (a component) is safe from critical hits while armored.

However, when the armor is stripped off a component on your 'mech, the items inside become vulnerable. Luckily, most shots won't do any critical damage; they'll just hurt your internal structure and increase the chance of that component being destroyed. However, 42% of shots will do damage to both your internal structure and some items in the component. The amount of damage dealt is based on weapon damage, according to the below:
58% of the time, no critical damage.
25% chance 1x weapon damage, dealt to a random available critical slot in the component.
14% chance 2x weapon damage, dealt in packets like the above to 2 random available critical slots (can be the same one)
3% chance 3x weapon damage.

A few special weapons deal extra critical damage. Break these out against exposed internals. They are the Machine Gun, Flamer, and LB 10-X AC. Be aware that the MG and Flamer are underpowered due to being essentially only good at this. Debate exists on the LBX (shotgun autocannon).
Special critical values
33% 0 crits
33% 1 crit
28% 2 crits
6% 3 crits

Most items have 10 HP, and will be destroyed upon accumulating 10 damage. Gauss Rifles and ECMs are particularly fragile. AC/20s are particularly durable... but this is offset by their large slot count, meaning they are likely to take crit hits.

Destroyed items do not work, and ammo bins have a 10% chance of detonation on being destroyed, leading to a happy pop-pop-pop that will shell the poor 'mech unless the explosion is vented by a CASE system. CASE will not protect the side torso it is in, but will prevent the damage from going on to kill the center torso. Damage will naturally progress toward the center of a 'mech, from Arm or Leg to Side Torso to Center Torso. Passing each barrier reduces damage by 50%.

Gauss Rifles also have a 90% chance of detonation, and do 20 damage. Gauss Rifle ammo itself is inert. When a component with a Gauss Rifle or Ammo Bin are destroyed (regularly, not critical damage) they still have the same chance to go up in smoke. Crits just make it happen earlier.

Implications of Critical Hit System
Scoring Critical Hits
Your best bet to score good critical hits is just to hammer weakened body parts. Anything packing a Gauss Rifle is a juicy target. LBXs are good at this, but so are any weapon with a high enough damage value that a single crit will destroy a component. These include PPCs, AC10s, Gauss Rifles, and AC/20s.

Defending against Critical Hits
Don't get shot. Also, "crit pad."

Crit Padding is when you make use of the "damage is dealt to a random hittable location" mechanic. If you have a Gauss Rifle as the only thing in a component, when the component takes a single AC/10 hit, you have a 38% chance of having a real bad day. If, however, you throw in a Double Heat sink and 2 tons of Gauss Ammo, you have a little more than half that chance. Whenever you have something explosive in a segment, try not to leave any empty slots there. And if you use Gauss, you really should use CASE.

All ACs have about 150 damage per ton of ammo. This means a single AC type for the 'mech will need 3-5 tons. If you have 2 types of AC, each needs 1-3 tons.

The below listed by increasing weight

AC/2:
+Long range,
+Excellent DPS per tonnage
+Rocks the enemy like a wagonwheel
+High projectile speed
-Terrible heat/damage ratio (for a ballistic... similar to missiles but still better than lasers)
-Damage scattered all over target
-Need lots of ammo due to damage inefficency

AC/5:
+Can be useful due to lowish weight and ability to aim shots
+Most heat efficient AC, so good if tight on heat and spare on tons
~Only useful if extremely skilled and using as direct fire support (high RoF sniper)
-Low DPS
-Sucks


UAC/5:
+Absurd DPS
+Best noise in game
~Generally similar pros and cons to AC/2. Pairs well with it.
-Biggest ammo-hog in game
-Jams make firepower unreliable. Best used if cover available to hid during jams. But boated, can just stand ground and press trigger.

LB10-X AC:
+Scattershot
+Good if you can't hit things
++Bonus to crit damage
+Lightish for job
-Scattershot
-Limited range
-Low striking power, DPS

AC/10:
+Biggest AC that can fit on arms with lower actuators (elbows, which allow horizontal arm articulation)
+Most versitile weapon in game except ML, with which it pairs nicely
+Style points
~Basically a bigger AC/5. Shorter range, more concentrated damage
-Generally better to trade up to AC/20, though you lose range
-Lowish DPS

AC20:
+20 f*ckin' points of m*therf*ckin' damage per hit
+2 head hits drops any 'mech in game (pairing these on a Jagermech or Cat K2 is often a good idea). Means auto-kill on Catapults that let you get to close range if you can nail your shots.
+High damage and low RoF great for popping in and out of cover
+Efficient kills mean you KS a lot, and use relatively little ammo. (Flipside: can't use damage score for E-Peening)
-Really easy to lose to critical hits
-Low projectile velocity and RoF means you have to be on top of your shots
-Really heavy
-Can't mount in a torso if have XL engine
-Can't mount in the arm of a 'mech with lower arm actuators (see note for AC/10).

Mechs that can mount an AC/20 in their arms:
Highlander 733C
Jagermech (all can mount 1 in each arm... result of using both is the dreaded "Jagerbomb")
Centurion YLW (Hero variant)
Raven 4X

Any 'mech with a ballistic hardpoint in the torso can mount an AC/20, but many are ill advised to use XL engines.

All of this said, try different weapons out and see what works for you. I love AC/10s, despite them being the 2nd weakest AC. My lancemate is even crazier: he uses a 4 AC/5 Cataphract 4X. Does amazing with it. Really nails his shots, because the AC/5 cooldown gives him a moment to line each up and fire with clicks rather than mashing. Each volley hits like an AC/20, and can reach out really far. But it's a very difficult build to pull off unless you really have a lot of faith in your ability to keep hitting the legs of jumping 'mechs at 1000m.

Oh, and remember that each ballistic still does damage out to almost 3x its max listed range! (Linearly less from it though.)

Unlike ACs, Laser weapons get more powerful as they get longer-range, though efficiency suffers. Important things to keep track of are DPS/ton and Damage/heat, which show efficiency in 'mechlab and when under high-heat conditions on the field. Energy weapons generally have superior DPS/ton to ballistics, but substantially worse damage/heat. NB: PPC line and flamers not in this Laser guide. They will appear later with their actual peers, respectively the Gauss (Sniper Weapons) and Flamer (Crit-Seekers).

The below listed by increasing weight and heat

Small Laser
+Insane DPS/ton
+Insane damage/heat for an energy weapon
+Weighs .5 tons, good for filling out load-outs
-Weak individually, which means hardpoints prevent too much boating of these
-Hardpoints mean these work better on smaller mechs (which have more HP/tons)
---Piss-poor range. Like really, really bad.

Small Pulse Laser
+Shortest burn time of lasers with hitscan means great accuracy for ankle-biters who want to take a shot and turn away
-Objectively the worst weapon in the game. Recently buffed, so not wholly inferior to the ML, but we'll have to see how it fares in the meta.

Medium Laser
+Most versatile weapon in game. Good combination of traits. I run it on essentially all of my builds as the standard back-up weapon. Hard to boat as a primary due to hardpoints, but great as a secondary. Some variants can boat for high heat but great short range power.
+Great DPS/ton
+Easy to hit lights
+Weighs 1 ton, 1 slot
-Fairly short range
-Hard to boat
-Heat gets up there in larger numbers

Medium Pulse Laser
+Slightly better heat/damage than ML
+Better at fitting into limited hardpoints (e.g. CT energy slots on CN9) than ML
+Faster burn time makes it really good for concentrating damage on scouts
-Substantially worse DPS/ton than ML
-Lower range than ML
-Inferior to ML except for specialty applications

Large Laser
+LL line is only way to get laser mechanic (easy to hit) with significant damage per hardpoint, making them popular with heavies and assaults
+Good range for a laser
-Way heavier than other laser models (at 5 tons 10x the SL, 5x the ML)
-Lacks the great efficiency that characterizes other lasers

Extended Range Large Laser (ERLL)
+Popular as a pinch sniper. Tonnage cheap way to get long range damage
-On paper and by stats, a terrible weapon. The efficiency you want from a laser is not here

Large Pulse Laser
+High damage with short burn and hitscan. Good for assault 'mechs looking for scout-hunting capability
-Really bad efficiency

Of course, use this only as an outline. Try out what weapons work for you. Stats aren't everything, as the popularity of the LL line shows. MPLs in particular have their fans, despite being kinda sub-optimal by the numbers.

Oh, and remember that each energy weapon still does damage out to almost 2x its max listed range! (Linearly less from it though, which decreases heat efficiency)

The favored weapons of the current meta, Sniper weapons make huge sacrifices in efficiency and stats for range, and high damage per strike at that range.

The below listed by increasing weight and heat

Suppression Weapons
AC/2
+A capable long range weapon with unusually good brawling capability
+Projectile speed and RoF give it a unique role as a targeting weapon: if you're leading right to hit with the AC/2, you'll land your PPC and GR shots.
+High DPS. In a long-range stand-and-fight scenario, the best weapon out there.
-Tiny damage packets mean that it is unsuited to Sniper work. Cannot duck in and out of cover, and damage tends to scatter across the target.

Large Laser and ER LL
+Longest range hitscan weapons. With burn time, makes them very accurate.
+Excellent for precision work, such as focusing down a weakened side torso, or attempting a headshot
+Great for anti-scout work at close range, for a long range weapon. Great at "sweeping the leg"
-Scattered damage
-Shorter range than the other weapons on this list

True Sniper Weapons
PPC
+Most generally useful sniper weapon, most favored weapon in current meta
+Especially when fired in groups, crazy damage per burst
+Heat limitation is mitigated if you can duck behind cover after each shot
+Remarkably fast cycle time allows serious DPS as heat allows
+Kills ECM for 3 seconds, allowing complete suppression of ECM with a single PPC and good enough shooting
-High heat, limiting usefulness in a brawl (where it's hard to find cover)
-Minimum range (damage falls of linearly from 10 at 90m to 0 at 0m) further limits usefulness in a brawl
-Draws a lot of attention fast. Flankers look for places emanating LRMs or PPC bolts as easy prey
-Large, high-heat energy weapon with projectile attack. This means that it doesn't pair great with MLs, the standard backup weapon. The synergy forces you into either SLs, MLs fired sparingly, SRMs, or SSRMs (with BAP if you don't have the heat to use PPCs to keep ECM negated)
-Boating requires insane amounts of DHS, and usually a big engine to help out. This often forces PPC boats into larger standard engines, which are really heavy

ER-PPC
+All listed for PPC
+NO MINIMUM RANGE. If you've got a good eye, you can drop scouts and flankers easily with the ER-PPC.
+Superior maximum range to PPC, among the longest in game
+No additional slots or tonnage compared to PPC
-Highest heat in game per shot, and bad efficiency to boot
-Heat exacerbates the biggest limitation of the PPC

Gauss
+Almost no heat at all
+Synergizes great with PPC or ML, for more sniper power or more backup flexibility
+Second highest damage per shot in game
+Ammo does not explode
+Does significant damage past a kilometer, and only drops off to 0 at around 2km. If you can hit it, you'll do good damage
-Ammo dependent
-Heaviest weapon in the game (mitigated by lack of heat requirements)
-Lot of slots
-Low hitpoints make it vulnerable to destruction
-Explodes for 15 damage 90% of the time on component or item destruction. In an XL 'mech or anything small, this has a decent chance of killing you outright
-Brawl with it, and prepare for a humiliating self-inflicted death

As usual, experiment to find your favorites!

Oh, and remember that each energy weapon still does damage out to almost 2x its max listed range! (Linearly less from it though, which decreases heat efficiency)

Ballistics drop off linearly to 3x effective range (the listed one). This is a notable advantage

Since it matters, here is a list of range data on long range weapons:
AC/2: ..…720……2,160
Gauss: …660……1,980 (better damage percentage than ER-PPC outside of around 1,250)
ER PPC:.810…….1,620
PPC:……540……1,080

With Centurions, you really get to pick from 2 options:

1) AC-based
Right arm cannon, backed up by CT lasers and streaks (the latter to fend off scouts). Uncommonly feature LRMs, but this is sub-optimal.

2) SRM-based
No cannon, but using multiple large SRM-packs. 3x6 is possible. Occasionally uses XL engine, particularly in CN9-D variant.

Be aware that these go for the A, D, and YLW variants. The AL is a different beast and can be set up as a scout hunter (lasers and streaks) or pinch sniper (2xPPCs in RA).

Never use a CN9 with a <250 engine rating. Max engine rating is preferable.

ZOMBIE CENTURIONS:
Cn9s can be really good "zombie 'mechs." This means they can limp around the battlefield on one leg, both side torsos and attached arms destroyed, and still put out respectable damage after the enemy has decided you aren't worth focusing on. This is because of (1) good hitboxes that soak damage and (2) all variants can pack 2 ML or MPL in the center torso, giving you moderate DPS way after you should be dead. The best zombie is actually the hero CN9-YLW, because it has superior torso twist to compensate for now having elbows. Mechs with XL engines obviously cannot zombie.

1. Use the local Champion 'mech. It'll be the trial 'mech with a (c ) after its name..
2. Stick with your team at all times, no matter what, unless you're leading 2:1 or more. And usually even then.
3. Try to always shoot at something other people are shooting at.
4. Generally, aim for center body mass. If you have FPS/Mechwarrior experience, try legging lights and zippy mediums.
5. http://mwo.smurfy-net.de/mechlab
6. Read other guides here and on the MWO forums!

This is a complicated question with complicated answers. Let's make it simple: get either a Catapult (CPLT) or a Jagermech (JM6). Both are useful, fun to level, and interesting in variants. Which of the two you want comes down to preference. I would generally recommend the JM6 if you have MechWarrior experience and/or prefer to be up close in the enemy's face. I would recommend the CPLT more generally to most new players. The specific variants you should start with are the...

CPLT-C1
+ Show Spoiler +
JM6-S
+ Show Spoiler +

In time, you can upgrade your mech to make it stronger. The order of upgrades you should get for the CPLT-C1 in particular is more or less the list of upgrades you should get for all 'mechs in general:
0. Rip out the Jump Jets. You aren't ready yet.
1. Double Heat Sinks...crucial on all 'mechs. shoot for a smurfy heat efficiency over 40. http://mwo.smurfy-net.de/
2. Endo Steel Structure...crucial for all non-assault 'mechs, and many of those too
3. XL 300 Engine...most useful engine in the game, though there are some 'mechs that can't or shouldn't run it. See my 'mechlab guide for more.
4. Artemis FCS...increases LRM power if you can see the target. Can be a matter of personal preference. I use it.
5. Jump Jets...add 'em back in. Try em out. Make 'em work.

1. Always get faster engine than stock
2. Always max armor
-No exceptions for lights. But for mediums/heavies/assaults, only 3/4 or 1/2 armor on legs is ok… unless you're going over 100 kph, piloting a CN9, or running with ammo in your legs. Then you should remove fairly little from the legs.
-Front/Back ratio should be 2:1 for scouts, 3:1 for most builds, and 4:1 for snipers
3. Always get Double Heat Sinks (DHS)
4. Usually get Endo Steel
5. Almost never get Ferro Fibrous, unless you have everything else you want and need more slots. It doesn't increase your armor cap, just slightly reduces your weight.
6. XL engines vary by 'mech. They are expensive, so get a 300XL and use it for everything that can fit it (swap it around, don't sell it. Only a handful of 'mechs can't take it.) With an XL, you die if you lose a side torso, but the XL is much lighter than the standard.

Good Mechs for an XL:
Any light: Commando, Jenner, Spider, Raven
Faster mediums: Cicada, Trebuchets
Big 'mechs with small side torsos: Catapult, Dragon, Kintaro
Bad Mechs for an XL:
Atlas, Awesome, Stalker (deceptively large side torsos)
Build Dependent Mechs:
Centurion:
SRM focused should get fast XL--note: cannot fit 300 except in CN9-D or YLW
AC/Laser focused should get fast Standard (except for assassin YLWs)
Cataphract, Jagermech
Really better not to go XL, but most builds require it for function.

Standard abreviations in MechWarrior/Battletech include:

H=Head (1 slot)
CT= Center Torso (2)
RT/LT= Right/Left Torso (12 standard, if XL engine, only 9)
CTR/RTR/LTR= Center/Right/Left Torso Rear (shares internals and slots with respective front section)
RL/LL= Right/Left Leg (2)
RA/LA= Right/Left Arm (slots complicated)

Slots in Arms:

10 Slots: Unarticulated Arms
Vertical Tracking only; cannot track horizontally beyond torso. Can mount more serious weaponry, such as dual UAC/5s or single AC/20s. 'Mechs with Unarticulated Arms are usually able to rotate their torsos farther than comparable 'mechs with Articulated Arms (including on the same chassis).
Mechs:
+ Show Spoiler +

9 Slots: Articulated Arms--No Hands
Horizontal and vertical tracking make for better aiming, particularly against faster targets. Tradeoff is less ability to mount some weapon setups.
Mechs:
+ Show Spoiler +

10/8 Slots: Mixed Articulation
Some 'mechs have an unarticulated RA but a fully articulated LA. These are generally variants of the 'mechs in the 9/8 category modified to be able to fit AC/20s in their RAs. Instead of having two arm reticles, they have very limited horizontal articulation (10deg).
Mechs:
+ Show Spoiler +

9/8 Slots: Articulated Arms--LA Hand only
Some 'mechs have a Left Hand but no Right. When melee is implemented, they will have a good LA punch to back up their RA weapons.
Mechs:
+ Show Spoiler +

8 Slots: Articulated Arms--With Hands
Currently, no advantage exists to 'mechs with hands. Eventually, hands will matter in the melee system, due to be part of the Solaris expansion, a year or so out from September release.
Mechs:
+ Show Spoiler +

Loadout Implications of Articulation
Some examples of the kinda of loadouts that are restricted by certain arrangements of actuators. Note that several of these loadouts are possible on only a single 'mech chassis, due to hardpoint restrictions. Always use Smurfy to check out possible loadouts.

Loadouts Exclusive to Unarticulated (10 slot) Arms:
Note that XL 'mechs cannot run these loadouts in their side torsos
+ Show Spoiler +

Loadouts Only Possible for Handless (10 or 9 slot) Arms:
+ Show Spoiler +

All energy weapons in the game do max damage between 0 and [listed range] meters, then drop off linearly to do 0 damage at 2x[listed range].

All ballistic weapons are the same, but only drop off to 0 at 3x listed range (giving them better range per listed number, though they compensate with lower acuracy).

Missile weapons just blow up at listed max range, doing no damage. LRMs have a 180m arming range.

In MechWarrior, MechCommander, or the board game version, Battletech, critical hits are one of the most important systems to understand. It is also one of the most misunderstood. This is how the MWO version works.

See those "slots" in the 'mechlab? Every Arm and Torso segment has 12, and every Head and Leg has 6, no matter what the 'mech is (a Commando at 25 tons and an Atlas at 100 have the same number of slots).

Some of those are filled by "built-in" equipment like engines, gyros, the cockpit, various actuators (joints). As of right now, these cannot take critical damage. This may change later on. The "dynamic slots" added by Endo or Ferro (never get Ferro before Endo) cannot take critical hits, and never will. CASE ammo storage cannot take critical damage.

Everything else on your 'mech can take critical damage: heat sinks, weapons, electronics, ammunition.

Your 'mech is protected by armor plating and internal structure. On your 'mech doll in the HUD, internal structure is the filling, and the armor is the shell. Critical hits cannot currently go through armor, so a mech segment (a component) is safe from critical hits while armored.

However, when the armor is stripped off a component on your 'mech, the items inside become vulnerable. Luckily, most shots won't do any critical damage; they'll just hurt your internal structure and increase the chance of that component being destroyed. However, 42% of shots will do damage to both your internal structure and some items in the component. The amount of damage dealt is based on weapon damage, according to the below:
58% of the time, no critical damage.
25% chance 1x weapon damage, dealt to a random available critical slot in the component.
14% chance 2x weapon damage, dealt in packets like the above to 2 random available critical slots (can be the same one)
3% chance 3x weapon damage.

A few special weapons deal extra critical damage. Break these out against exposed internals. They are the Machine Gun, Flamer, and LB 10-X AC.

Most items have 10 HP, and will be destroyed upon accumulating 10 damage. Gauss Rifles and ECMs are particularly fragile. AC/20s are particularly durable... but this is offset by their large slot count, meaning they are likely to take crit hits.

Destroyed items do not work, and ammo bins have a 10% chance of detonation on being destroyed, leading to a happy pop-pop-pop that will shell the poor 'mech unless the explosion is vented by a CASE system. CASE will not protect the side torso it is in, but will prevent the damage from going on to kill the center torso. Damage will naturally progress toward the center of a 'mech, from Arm or Leg to Side Torso to Center Torso. Passing each barrier reduces damage by 50%.

Gauss Rifles also have a 90% chance of detonation, and do 20 damage. Gauss Rifle ammo itself is inert. When a component with a Gauss Rifle or Ammo Bin are destroyed (regularly, not critical damage) they still have the same chance to go up in smoke. Crits just make it happen earlier.

Update
The recent buffs to MGs and LBX ACs have made them far better at scoring critical hits.

Also 15% of critical hit damage now harms internal structure as well. This has made the LBX and MG very powerful against exposed internals.

Implications of Critical Hit System
Scoring Critical Hits
Your best bet to score good critical hits is just to hammer weakened body parts. Anything packing a Gauss Rifle is a juicy target. LBXs are good at this, but so are any weapon with a high enough damage value that a single crit will destroy a component. These include PPCs, AC10s, Gauss Rifles, and AC/20s.

Defending against Critical Hits
Don't get shot. Also, "crit pad."

Crit Padding is when you make use of the "damage is dealt to a random hittable location" mechanic. If you have a Gauss Rifle as the only thing in a component, when the component takes a single AC/10 hit, you have a 38% chance of having a real bad day. If, however, you throw in a Double Heat sink and 2 tons of Gauss Ammo, you have a little more than half that chance. Whenever you have something explosive in a segment, try not to leave any empty slots there. And if you use Gauss, you really should use CASE.

All ACs have about 150 damage per ton of ammo. This means a single AC type for the 'mech will need 3-5 tons. If you have 2 types of AC, each needs 1-3 tons.

The below listed by increasing weight

AC/2:
+Long range,
+Excellent DPS per tonnage
+Rocks the enemy like a wagonwheel
+High projectile speed
-Terrible heat/damage ratio (for a ballistic... similar to missiles but still better than lasers)
-Damage scattered all over target
-Need lots of ammo due to damage inefficency

AC/5:
+Can be useful due to lowish weight and ability to aim shots
+Most heat efficient AC, so good if tight on heat and spare on tons
~Only useful if extremely skilled and using as direct fire support (high RoF sniper)
-Low DPS
-Sucks


UAC/5:
+Absurd DPS
+Best noise in game
~Generally similar pros and cons to AC/2. Pairs well with it.
-Biggest ammo-hog in game
-Jams make firepower unreliable. Best used if cover available to hid during jams. But boated, can just stand ground and press trigger.

LB10-X AC:
+Scattershot
+Good if you can't hit things
++Bonus to crit damage
+Shreds internal structure
+Lightish for job
+Rocks them enemy like a wagonwheel
-Scattershot
-Limited range
-Low striking power, DPS

AC/10:
+Biggest AC that can fit on arms with lower actuators (elbows, which allow horizontal arm articulation)
+Most versitile weapon in game except ML, with which it pairs nicely
+Style points
~Basically a bigger AC/5. Shorter range, more concentrated damage
-Generally better to trade up to AC/20, though you lose range
-Lowish DPS

AC20:
+20 f*ckin' points of m*therf*ckin' damage per hit
+2 head hits drops any 'mech in game (pairing these on a Jagermech or Cat K2 is often a good idea). Means auto-kill on Catapults that let you get to close range if you can nail your shots.
+High damage and low RoF great for popping in and out of cover
+Efficient kills mean you KS a lot, and use relatively little ammo. (Flipside: can't use damage score for E-Peening)
-Really easy to lose to critical hits
-Low projectile velocity and RoF means you have to be on top of your shots
-Really heavy
-Can't mount in a torso if have XL engine
-Can't mount in the arm of a 'mech with lower arm actuators (see note for AC/10)
-Heat penalty kicks in if you use 2 of these within 0.5 sec. Use chain fire.

Mechs that can mount an AC/20 in their arms:
Highlander 733C
Jagermech (all can mount 1 in each arm... result of using both is the dreaded "Jagerbomb")
Centurion YLW (Hero variant)
Raven 4X

Any 'mech with a ballistic hardpoint in the torso can mount an AC/20, but many are ill advised to use XL engines.

All of this said, try different weapons out and see what works for you. I love AC/10s, despite them being the 2nd weakest AC. My lancemate is even crazier: he uses a 4 AC/5 Cataphract 4X. Does amazing with it. Really nails his shots, because the AC/5 cooldown gives him a moment to line each up and fire with clicks rather than mashing. Each volley hits like an AC/20, and can reach out really far. But it's a very difficult build to pull off unless you really have a lot of faith in your ability to keep hitting the legs of jumping 'mechs at 1000m. Edit: this insane build has actually become quite popular lately. Try it out and see for yourself!

Oh, and remember that each ballistic still does damage out to almost 3x its max listed range! (Linearly less from it though.) I generally will still fire out to double my listed range unless ammo conservation demands otherwise.

Unlike ACs, Laser weapons get more powerful as they get longer-range, though efficiency suffers. Important things to keep track of are DPS/ton and Damage/heat, which show efficiency in 'mechlab and when under high-heat conditions on the field. Energy weapons generally have superior DPS/ton to ballistics, but substantially worse damage/heat. NB: PPC line and flamers not in this Laser guide. They will appear later with their actual peers, respectively the Gauss (Sniper Weapons) and Flamer (Crit-Seekers).

The below listed by increasing weight and heat

Small Laser
+Insane DPS/ton
+Insane damage/heat for an energy weapon
+Weighs .5 tons, good for filling out load-outs
-Weak individually, which means hardpoints prevent too much boating of these
-Hardpoints mean these work better on smaller mechs (which have more HP/tons)
---Piss-poor range. Like really, really bad.

Small Pulse Laser
+Shortest burn time of lasers with hitscan means great accuracy for ankle-biters who want to take a shot and turn away
-The same size as the ML, which is generally better

Medium Laser
+Most versatile weapon in game. Good combination of traits. I run it on essentially all of my builds as the standard back-up weapon. Hard to boat as a primary due to hardpoints, but great as a secondary. Some variants can boat for high heat but great short range power.
+Great DPS/ton
+Easy to hit lights
+Weighs 1 ton, 1 slot
-Fairly short range
-Hard to boat
-Heat gets up there in larger numbers

Medium Pulse Laser
+Slightly better heat/damage than ML
+Better at fitting into limited hardpoints (e.g. CT energy slots on CN9) than ML
+Faster burn time makes it really good for concentrating damage on scouts
-Substantially worse DPS/ton than ML
-Lower range than ML
-Inferior to ML except for specialty applications

Large Laser
+LL line is only way to get laser mechanic (easy to hit) with significant damage per hardpoint, making them popular with heavies and assaults
+Good range for a laser
-Way heavier than other laser models (at 5 tons 10x the SL, 5x the ML)
-Lacks the great efficiency that characterizes other lasers

Extended Range Large Laser (ERLL)
+Popular as a pinch sniper. Tonnage cheap way to get long range damage
-On paper and by stats, a terrible weapon. The efficiency you want from a laser is not here

Large Pulse Laser
+High damage with short burn and hitscan. Good for assault 'mechs looking for scout-hunting capability
-Really bad efficiency

Of course, use this only as an outline. Try out what weapons work for you. Stats aren't everything. MPLs in particular have their fans, despite being kinda sub-optimal by the numbers.

Oh, and remember that each energy weapon still does damage out to almost 2x its max listed range! (Linearly less from it though, which decreases heat efficiency)

The favored weapons of the current meta, Sniper weapons make huge sacrifices in efficiency and stats for range, and high damage per strike at that range.

The below listed by increasing weight and heat

Suppression Weapons
AC/2
+A capable long range weapon with unusually good brawling capability
+Projectile speed and RoF give it a unique role as a targeting weapon: if you're leading right to hit with the AC/2, you'll land your PPC and GR shots.
+High DPS. In a long-range stand-and-fight scenario, the best weapon out there.
-Tiny damage packets mean that it is unsuited to Sniper work. Cannot duck in and out of cover, and damage tends to scatter across the target.

Large Laser and ER LL
+Longest range hitscan weapons. With burn time, makes them very accurate.
+Excellent for precision work, such as focusing down a weakened side torso, or attempting a headshot
+Great for anti-scout work at close range, for a long range weapon. Great at "sweeping the leg"
-Scattered damage
-Shorter range than the other weapons on this list

True Sniper Weapons
PPC
+Most generally useful sniper weapon, most favored weapon in current meta
+Especially when fired in groups, crazy damage per burst
+Heat limitation is mitigated if you can duck behind cover after each shot
+Remarkably fast cycle time allows serious DPS as heat allows
+Kills ECM for 3 seconds, allowing complete suppression of ECM with a single PPC and good enough shooting
-High heat, limiting usefulness in a brawl (where it's hard to find cover)
-Minimum range (damage falls of linearly from 10 at 90m to 0 at 0m) further limits usefulness in a brawl
-Draws a lot of attention fast. Flankers look for places emanating LRMs or PPC bolts as easy prey
-Large, high-heat energy weapon with projectile attack. This means that it doesn't pair great with MLs, the standard backup weapon. The synergy forces you into either SLs, MLs fired sparingly, SRMs, or SSRMs (with BAP if you don't have the heat to use PPCs to keep ECM negated)
-Boating requires insane amounts of DHS, and usually a big engine to help out. This often forces PPC boats into larger standard engines, which are really heavy
-Limit 2 per volley unless you want to burn up

ER-PPC
+All listed for PPC
+NO MINIMUM RANGE. If you've got a good eye, you can drop scouts and flankers easily with the ER-PPC.
+Superior maximum range to PPC, among the longest in game
+No additional slots or tonnage compared to PPC
-Highest heat in game per shot, and bad efficiency to boot
-Heat exacerbates the biggest limitation of the PPC

Gauss
+Almost no heat at all
+Synergizes great with PPC or ML, for more sniper power or more backup flexibility
+Second highest damage per shot in game
+Ammo does not explode
+Does significant damage past a kilometer, and only drops off to 0 at around 2km. If you can hit it, you'll do good damage
-Ammo dependent
-Heaviest weapon in the game (mitigated by lack of heat requirements)
-Lot of slots
-Low hitpoints make it vulnerable to destruction
-Explodes for 15 damage 90% of the time on component or item destruction. In an XL 'mech or anything small, this has a decent chance of killing you outright
-Brawl with it, and prepare for a humiliating self-inflicted death

As usual, experiment to find your favorites!

Oh, and remember that each energy weapon still does damage out to almost 2x its max listed range! (Linearly less from it though, which decreases heat efficiency)

Ballistics drop off linearly to 3x effective range (the listed one). This is a notable advantage

Since it matters, here is a list of range data on long range weapons:
AC/2: ..…720……2,160
Gauss: …660……1,980 (better damage percentage than ER-PPC outside of around 1,250)
ER PPC:.810…….1,620
PPC:……540……1,080

With Centurions, you really get to pick from 2 options:

1) AC-based
Right arm cannon, backed up by CT lasers and streaks (the latter to fend off scouts). Uncommonly feature LRMs.

2) SRM-based
No cannon, but using multiple large SRM-packs. 3x6 is possible. Often uses XL engine, particularly in CN9-D variant.

Be aware that these go for the A, D, and YLW variants. The AL is a different beast and can be set up as a scout hunter (lasers and streaks) or pinch sniper (2xPPCs in RA).

Never use a CN9 with a <250 engine rating. Max engine rating is preferable.

ZOMBIE CENTURIONS:
Cn9s can be really good "zombie 'mechs." This means they can limp around the battlefield on one leg, both side torsos and attached arms destroyed, and still put out respectable damage after the enemy has decided you aren't worth focusing on. This is because of (1) good hitboxes that soak damage and (2) all variants can pack 2 ML or MPL in the center torso, giving you moderate DPS way after you should be dead. The best zombie is actually the hero CN9-YLW, because it has superior torso twist to compensate for now having elbows. Mechs with XL engines obviously cannot zombie.

YEN-LO-WANG ASSASSIN BUILD:
Normally, the YLW is run with a standard engine to optimize zombie power. But what if you throw caution to the wind and run around at 107 kph with your AC/20, blasting away like a maniac? A lot of fun, actually. I have my highest KDR in this configuration, using my AC/20 and MPL to precision strike 'mechs in the back, focus damage on one body part, and cripple or destroy the enemy before he has a chance to return fire. In a turn fight, you can actually stay out of the firing arcs of any assault or heavy, and many mediums. Make sure to aim your shots, because your advantage is the damage you can put on a single point… your DPS is actually fairly low.