[Al B. Drinkinbeer]

Yep - it's called clipping. It's a graphical glitch where the gun barrell, arm, dead body part will stick through a wall sometimes. I've seen it in other games also. When I'm hiding (camping? hehe) I try to avoid sticking my gun at the wall if I'm right up on it to avoid it poking thru the other side, thus giving away my position. I don't beleive a gun barrell glitching through a wall can shoot through said wall...