Charnier's hitman Pierre Nicoli (Marcel Bozzuffi) carries a Colt Gold Cup National Match as his sidearm throughout the film, notably using it to hijack the BMT West End Line elevated train.
Colt Detective Special
Many of the NYPD detectives, including Jimmy "Popeye" Doyle (Gene Hackman), Walt Simonson (Eddie Egan, the real life basis for Doyle), and FBI agent Bill Mulderig (Bill Hickman), carry Colt Detective Specials. Doyle keeps his in an ankle holster, although it switches in several scenes to a Smith & Wesson Model 36. Several of Boca's mobsters, including his brother Lou (Benny Marino), also use Detective Specials.
Smith & Wesson Model 36
Due to continuity errors, some shots of Det. "Popeye" Doyle (Gene Hackman) pursuing Nicoli after the car chase and searching for Charnier after the bust, his Colt Detective Special is now a Smith & Wesson Model 36. Salvatore "Sal" Boca (Tony Lo Bianco) and some of his mobsters also fire Model 36s at the NYPD.
One of Boca's mobsters fires at the NYPD with a Beretta Model 70.
Shotguns
Winchester Model 1897
Det. Buddy "Cloudy" Russo (Roy Scheider) and several other NYPD officers fire Winchester Model 1897 shotguns at the mobsters and drug dealers during the final shootout.
During the final shootout several of the other NYPD officers appear to be using the Ithaca 37 shotgun. The Ithaca 37 was used by the NYPD for several decades, including the 1970s.