Red Faction

Note: All weapon-related trophies count across all saves. If you want you can make a save near enemies, kill them, reload the save and repeat the process for every trophy.

The Heavy Machine Gun is one of the late-game weapons and is dropped by mercenaries. Much like the Sniper Rifle, this doesn't auto-lock on to enemies like other guns but this isn't a huge hindrance due to how powerful it is. You will get these in surplus when the mercenaries arrive so you should get this easily as long as you use the weapon.