Colt 1921 Thompson .45 ACP, Transferable Machine Gun, All Original

Mass
10.8 lb (4.9 kg) empty (Thompson M1928A1)
10 lb (4.5 kg) empty (Thompson M1A1)

Length
33.7 in (860 mm) (M1928A1 with compensator)
31.9 in (810 mm) (M1/M1A1)
Barrel length
10.52 in (267 mm)
12 in (300 mm) (with Cutts compensator)

Cartridge
.45 ACP (11.43×23mm)
10mm Auto (Limited quantity of FBI conversions)

Action Blowback, Blish Lock

Rate of fire
approx. 700–800rpm (M1928),
approx. 600-700rpm (M1A1),
approx.900 rpm (M1921)
approx. 1500 rpm (Annihilator)

Muzzle velocity 935 ft/s (285 m/s)

Effective firing range 164 yds (150 m)

Feed system
20-round stick/box magazine 0.4 lb (0.2 kg) unloaded
30-round stick/box magazine 0.5 lb (0.2 kg) unloaded
50-round drum magazine 2.6 lb (1.2 kg) unloaded
100-round drum magazine
(M1 and M1A1 models do not accept drum magazines)