I think a EMP grenade would be better against nanomachines, or your own nanoswarms. An acid gas could be another useful idea to melt at least most of the moving parts. Personally, I don't like the energy weapons of the setting, the look to me as heavy weaponry, and my players are more prone to retreat when faced by heavy opposition than to engange, and kinetic weapons are much easy to acquire, mantain and keep anonymous. I think what you want is to turn the plasma weapon into a sort of plasma machinegun, to kill lots and lots of nanomachines. While it looks heroic, it's less effective than the flamethrowing idea previously presented by arenamontanus, since you won't be able to kill all the nanobuggers ever... while with the flamethrower design you might have a chance of doing so.. In essence, what you need to do to transform the plasma thrower is Hardware: Armorer (COG), maybe supported by Knowledge: Physics or Knowledge: Beam weapons (or even better, Knowledge: Plasma), and then turn the weapon into a spray weapon that rolls with the Beam Weapons skill. CONS: Low ammo (10 shots... unlikely to be increased by turning into a flamethrower), high PEN and damage for a weapon devoted to nanoswarm-killing (overkill!), two-hands weapon, heavy weight, exceedingly prone to friendly fire situations as an area weapon. PROS: the cooling problems only occur in vacuum (derived from the absence of movement, thus the heat remains around the weapon much more time than in an atmospheric enviroment). My advice would be to ADD a flamethrowing mode to the weapon, so you can use it as the vanilla mode, and swith as a free action to flamethrowing mode (using then the Spray Weapons skill, to maximize damage and avoid hitting friends), using a whole charge to produce a really big ball of plasma. By the way, keep in mind that TITAN-level nanomachines are much more advanced and less limited than the ones avaiable to players (for startes, TITAN nanoswarms can self-replicate, while the transhuman ones are designed not to self-replicate), so in theory anything the GM wants, they can resist.