Gangsta style for reference
I don't have a problem with the way the guns are held. It looks fine to me, they seem to be aiming right ahead and everything.
WAITAMINUTE I THINK I JUST FIGURED IT OUT. Do you have your minifigs' hands upside down? as in, with the curved part on the top of the hand instead of on the bottom? because when it's on top then yes, the stock bangs into their arm all stupid and it looks bad. Otherwise, with the hand facing the other way it appears to be a pretty snug fit to me.
Is what I'm talking about.