the gangs have guns, yes, but making it easier for them to acquire the guns and without being able to disarm them legally will not have a positive effect.
I don't watch Tru-cop or whatever so i cannot speak to that, but long guns are not the main problem. if someone is walking around with one of them, it is noticeable.
If the police are being attacked with automatic weapons routinely, then i think we need our national guard at home and not in iraq until we get things squared away in the U.S.
I imagine it happens in some circumstances, but i think it is rather uncommon and gets met with overwhelming force in short order.