But why would a helicopter mounted GAU-17 need a compensator?It's a flash hider, for what it's worth :\
Because it's not a helicopter-mounted GAU17 did you even read the post
What the heck's a heat guardIt's a compensator, it's used to add weight to the end of the barrel to reduce recoil and hopefully a bit of the muzzle flash.
omg i need that picture