Gunshot wound to the shoulder?
So, I've got a story where two men go into an old abandoned train yard in Detroit(which I've got a Dtroit-ian helping me on, accuracy-wise) that's known for gang activity. One of the men is a more hand-to-hand fighter, who ends up off doing his own thing beating the shit out of people and disarming them. The other is guns and ammo's poster child and trying to shoot and kick everything out of hisway, killing all in his path. As they're fighting, someone from the roof of a second story building behind them shoots mister guns and ammo from behind. I want the wound to be incapacitating for about a couple of weeks, nothing TOO serious, but one that would mean the other man would have to take care of him for a bit, as he wouldn't be able to use his arm too well.
Here are my questions, any help would be appreciated:
What sort of gun should the shooter be using to hit a man in the back(the left shoulder)?
Of course, depending on the rifle, how bad would he get hurt to show the signs and have the symptoms I'm talking about. I don't want there to be any serious permanent damage, just one that's going to decommission him.
If you have any questions, I'll answer what I can and give the details :) Thanks in advance!!