Pretty Boy Floyd
Pretty Boy Floyd is a 1960 gangster film that was one of many shoestring-budget gangster films made in the late 1950s and early 1960s, that would feature in the cast a number of unknown actors, some of whom (in this case Barry Newman, Al Lewis, and Peter Falk) went on to be relatively famous. Although taking many historical liberties (such as renaming most of the people involved), it is a generally accurate depiction of the life of 1930s bank robber Charles "Pretty Boy" Floyd.
The following weapons were used in the film Pretty Boy Floyd:
Mannlicher M1895 KNIL No. 1 Carbine
Jed Watkins (Roy Fant) can be seen with a Mannlicher M1895 KNIL No. 1 Carbine when Floyd returns home for the first time in six years. It is one of the guns later donated to Floyd. Despite this, Jed produces another identical rifle (likely the same prop) when Floyd returns again.
Colt New Service
Charles "Pretty Boy" Floyd (John Ericson) uses a Colt New Service when he shoots his neighbor Grindon to avenge his father's murder. The sheriff, Blackie Faulkner (Jason Evers) also carries a New Service.
Colt Detective Special
"Pretty Boy" Floyd (John Ericson) typically brandishes a set of Colt Detective Special revolvers (unlike the actual Floyd who always carried two M1911A1s). Shorty Walters (Peter Falk) also uses two Colt Detective Specials during the Ohio bank robbery. Floyd's fellow bank robber Baker (Philip Kenneally) uses a Detective Special against the Courtney brothers. The Kansas City mob bosses use a Detective Special when determining the fate of Floyd, Al, and Manny.
Smith & Wesson Model 36
In addition to a Detective Special, "Pretty Boy" Floyd (John Ericson) hides a Smith & Wesson Model 36 under his pillow in Ohio. The police grab it from him before he gets a chance to use it. (This gun would be anachronistic for the film as it wasn't developed until 1950).
Colt Police Positive
"Pretty Boy" Floyd (John Ericson) carries two Colt Police Positive revolvers during his first bank robbery in Sylvan, Ohio with Shorty and when he robs his hometown bank in Sallisaw. One of them has a sawn-down barrel, as evident by its lack of a front sight. An Ohio policeman that shoots at Floyd during the finale also carries a Police Positive.
Carl Gustav M/45
"Pretty Boy" Floyd (John Ericson) shows Curly Winwell (Carl York) a Carl Gustav M/45 submachine gun he got from "the big city". This is a complete anachronism, since the Carl Gustav Swedish Submachine Gun was not developed until 1945, a full 12 years after the events portrayed in the film. Also historically the gang stole much of their firepower from local police armories, so any submachine gun would be a domestic model, like a Thompson.
The weapon pictured seems to have a strange wooden stock instead of the normal steel frame. The barrel looks like the one used for firing blanks. It is usually silver painted and has threads that comes out in front of the cooling shroud. It also has a narrower caliber to partially break up the plastic bullets before they hit the (here missing) stopper at the barrel end.
This weapon seems to lack the internal parts since there is no cocking handle, bolt or spring. The magazine is missing too.
"Pretty Boy" Floyd (John Ericson) fires a M1A1 Thompson during one of the film's montages. Al Riccardo (Barry Newman) takes one when he tries to run away from Floyd in the end. The lawman that shoots Floyd down uses a Thompson. The M1A1 has a Cutts compensator and, in some scenes, has a vertical foregrip added to make it match the more period-accurate M1928 (as the M1A1 is anachronistic).