A vote for "Cotton Comes to Harlem" for revolver work - and a few autos too. Even without the fight scenes there is an absolute classic "turn in your guns and badges" scene that leaves the commander's desk literally buried under guns. (No way two guys could have carried that much hardware without wheelbarrows, but still fun.)
Also a flick called I believe "Hickey and Boggs" with Robert Culp and Bill Cosby more or less reprising their "I Spy" shtick as private eyes using a M-29 S&W and a Colt Official Police ? successfully against goons with an M-60.