M-99 EVAW

M-99 Extra-Vehicular-Activity Weapon is the signature weapon of the USAF EVATs, the astronaut troops of the U.S. Aerospace Force. The weapon is a cumbersome monstrosity with two barrels, two massive magazines, and a co2 booster tank strapped to the EVA Trooper's belt. It fires two kinds of self-propelled rounds, using the compressed gas to eject the rounds from the barrel before their rocket propulsion ignites. The first round is a 12mm seeking slug that homes in on infrared and radar sensors (it's quite expensive); in addition, there is an IFF reader in the shell to prevent it from tracking on friendly targets. The second round is a standard 25mm high explosive grenade fitted with a small rocket booster and a proximity fuse. Both rounds are equipped with an end-of-range self-destruct charge, which destroys the round when it goes beyond a set range (usually 10% beyond maximum range at velocity>. The advantages of the EVAW are low recoil, no heat emission, low gas ejection (standard rounds produce a cloud of smoke in zero-g/zero-pressure atmosphere), practically no moving parts, and built-in accuracy. Admittedly, it's not as perfect a space weapon as a portable laser, but it's almost as good. Grenade rounds cost 50eb, rocket rounds cost 125eb.

Source

 * Deep Space, pg.58
 * Home of the Brave, pg.83