You may have noticed that, generally speaking, I am not terribly kind to Plasma Cannons. Plasma Cannons are the red-headed stepchild of energy weapons in BattleTech, doing 0 actual damage and having their main niche be in countering Tanks and Infantry, which are uncommon to see on tables and really aren’t that strong. Plasma Cannons are, in theory, a great crowd control piece against mechs as well. They inflict 2d6 heat on any mech they hit, which is situationally very good.
The problem is that the best form of crowd control is death, and Plasma Cannons don’t actually directly help you kill enemy mechs. For 170 BV plus ammo, you are spending more BV than a PPC to do 0 actual damage instead of 10. Plasma Cannons have decent range, are pretty light and easy to squeeze into a design even with ammo, and would be a contender for best weapon in the game if they did even 5 points of actual damage. This is all in isolation though, and there are a lot of really awesome use cases for a Plasma Cannon, but a lot of mechs just do not make effective use of them. The Plasma Cannon isn’t bad, it’s just misunderstood.
Bad Plasma Cannon Usage
The thing that marks a bad Plasma Cannon mech is the Plasma Cannon being treated as a main gun. Mechs like the Grendel F mount few weapons other than their Plasma Cannons and cost a ton, leaving you with a mech that can overheat an enemy but struggle to follow up on that heat themselves. Most of these Plasma Cannon mechs seem to be built as dedicated support pieces, designed to overheat an enemy and then let a heavier friend finish them off. The issue is that a Plasma Cannon inflicts the same amount of heat as an SRM 6 loaded with inferno ammo while costing nearly 4 times as much. If you are a light/fast mech, such as an Ice Ferret L, you would be better served with an SRM-6 or two. It would let you inflict the same amount of heat while also being a weapon that can swap to ammo that actually does damage, and is more flexible in general.
Plasma Cannons are a waste on light mechs and fast mechs, as they have the speed to make use of Inferno SRMs. A Javelin 10N inflicts the same amount of heat damage as a Grendel F, while being slightly slower and costing only around 600 BV, instead of nearly 2000. As dedicated support mechs, Plasma Cannon mechs fail by being just as expensive as the mechs they are supporting. The best support pieces in BattleTech are the ones that are dirt cheap. If you are taking a unit purely for the utility it serves assisting other units, you don’t want to spend tons of BV on it because if it loses it’s operating buddy, it is very, very sad. That said, something like a Javelin 10N is actually fully capable of following up on it’s own heat damage, as it still has a pair of SRM-6s and you can load a ton of regular ammo along with your infernos so that you can actually do some damage to anything you overheat. Dedicated Plasma Cannon mechs are therefore kind of bad, usually lacking that follow up and costing a ton of BV.
Good Plasma Cannon Usage
The best way to use a Plasma Cannon, and the best Plasma Cannon mechs, are ones that have their own support. Mechs like the Gargoyle P mount Plasma Cannons in combination with other heavy weapons, in the P’s case a pair of large pulse lasers. Using the Plasma Cannon as effectively a Coaxial weapon with another large gun is very effective because, while it is a lot of BV, you have a mech that can both CC another mech with 2d6+ heat a turn and follow up on that advantage on its own. I do understand that you need to look at mechs in their role in a force, not just in isolation, but the Grendel F and Gargoyle P are both very expensive, about 2000 and about 2400 respectively, but the Gargoyle P has the capabilities to follow up on it’s own crowd control in a way that the Grendel F can struggle to.
The reason that I generally consider the Plasma Rifle to be a better weapon is that it has that follow up baked in. You trade half the heat damage for 10 physical damage, and that means that you get the crowd control and the damage to exploit that crowd control at the same time. Plasma Cannons need to be mounted along with weapons that do actual damage to replicate the same thing, and that is why a lot of Plasma Cannon mediums and lights come up short. They just lack the tonnage to carry extra weapons. Something like a Loki MkII D that has the tonnage to carry both the Plasma Cannons as well as significant other primary weapons will absolutely rip, overheating enemies or forcing them to reduce their damage output to not cook alive as it pummels them to death with LRMs and lasers.
Inferno SRMs will still do the same job for much cheaper, but on larger mechs, such as the Loki MkII or Gargoyle P, they can struggle to close in to a close enough range to make use of Inferno SRMs. 3 hexes is very short, and if you are consistently able to get a 4/6 mech within 3 hexes of the enemy you are a rare person. On those bigger, slower mechs, they just can’t use Inferno SRMs because they will very rarely get the chance to fire them without a to-hit penalty. The Plasma Cannon’s boosted range is huge for those sort of big, slow moving loser mechs, as it lets them tag an enemy at a good range, slow them down from heat penalties, and then slowly walk up like a horror monster closing in on a loser teenager caught in a trap. It is genuinely powerful and I am upset I didn’t catch this synergy sooner.
The realization that Plasma Cannons are best used as support tools mounted on heavy and assault mechs, rather than as annoyance devices mounted on crappy lights, is a huge step towards using them effectively. I have actually had my opinion of Plasma Cannons significantly rehabilitated by this realization, and think that they might be some of the best weapons in the game if mounted on a mech that can follow up on the slows, bad accuracy, and possible shutdowns that they can force on unwary opponents. The Loki MkII D is my current pick for best Plasma Cannon mech in the game, but with 7000 variants spread across like 1000 mechs I am sure there is a better one hiding on some random Clan Burrock mech or something that I just haven’t ever heard of.
Cheers.
