All the guns in the game are based on actual firearms. The following is a list of the guns in the game and their closest real-life equivalents:

.38 Snub-Nose: Colt Detective .38 Special / Smith & Wesson M & P 2 in revolver
Pistol: Colt M1911A1 semi-auto .45 pistol
Magnum: Smith & Wesson Model 10 revolver in .357
Long-barrel Shotgun: Remington 870 pump-action shotgun
Tommy Gun: Thompson M1921 / 1928 sub-machine gun in .45