Quite frankly, it's an incredible movie. VERY tight story about cops in LA in the 1950s investigating corruption.
It very faithfully captures the feel of the 1950s Film Noir except for the fact that it's in color.
The gun fight scenes are VERY realistic in that they actually aim, are shown reloading, and don't have guns that fire 300 shots before requiring a reload.
Guns in the movie include:
Handguns -- Colt 1911s, Colt Detective Specials, a small-frame S&W, and the bad guy at the end appears to be carrying a Smith Military & Police. The bad guy also has a scene with, I believe, a Colt in either .32 or .380 ACP.
Shotguns -- I believe all the shotguns are actually Ithacas. They seem to all have the Ithaca bottom load, bottom ejection and the unique under-barrel stud that locks the barrel to the action. One of the bad guys MAY have a Winchester in the shoot-out at the end.
Submachine Gun -- You don't see it, but you hear it. Probably a Thompson.
No rifles that I can remember.
My only gripe is that the shotguns especially had little to no "recoil."