One of the hoods sent by Joey Zasa to kill Vincent Mancini (Andy Garcia) carries a Beretta Cheetah, which Vincent disarms him of and uses to shoot both hoods. (Although the pistol turns into an Astra Constable for a close-up).
For the close-up in which Vincent shoots the thug through the head, an Walther PP replaces the Beretta Cheetah. Al Neri (Richard Bright) is also given a Walther PP to assassinate Archbishop Gilday.
The helicopter hitmen sent by Joey Zasa (Joe Mantegna) to kill Michael Corleone (Al Pacino) and other mob bosses at the Atlantic City meeting carry Uzi submachine guns.
Several 12 Gauge Double Barreled Shotguns with exposed hammers can be seen. Al Neri (Richard Bright) uses one to blast out of the Atlantic City meeting, one of Vincent's hitmen uses one during the street parade shooting, Mosca (Mario Donatone) uses one when shooting at Don Tommasino's car, and some of the actors during Anthony's opera in Sicily can be seen handling some.
Armand (Rogerio Miranda) and Francesco (Carlos Miranda), the twins employed by Michael as bodyguards, carry black semi-automatic pistols.
It must be a Beretta 1951. It can't be the 1951, the 1951's barrel goes pretty far out beyond the frame, it just barely protrudes in the screencaps, probably a 951. The Godfather 3 is set in the late 70's through the early 80's, meaning that the twins could be carrying 92's or 92SB's. maybe but it almost looks like a single stack mag.
