CODE – 02-132-928

NAME – M1928AC Thompson

NAME (NATIVE) –Gun, Submachine, Cal. .45, U.S. Navy Model of 1928, Thompson Model of 1928AC

COMMON NAMES – US Navy “Overstamp”

COUNTRY OF ORIGIN – USA

DATE OF MANUFACTURE – 1928 (Standardized by Navy March 1932)

CALIBER – 11.43x23mm (.45 ACP)

OVERALL LENGTH – 80.8 cm (31.8 in)

Removing stock takes 21.6 cm (8.5 in) off of overall length

BARREL LENGTH – 26.7 cm (10.5 in), 37.6 cm (12.44 in) with Cutts compensator

RIFLING (TYPE & TWIST) – 6 Groove, Right hand twist, one turn in 41 cm (16 in)

BULLET DIAMETER – 11.46 mm (0.451 in)

BULLET WEIGHT – 15 g (230 grain)

MUZZLE VELOCITY – 290 m/s (950 fps)

MUZZLE ENERGY – 625 j (451 ft/lbs)

WEIGHT (EMPTY) WITHOUT STOCK – 4.04 kg (8 lb 14.5 oz) with Vertical foregrip, Cutts Compensator

WEIGHT (EMPTY) WITH STOCK – 4.84 kg (10 lb 5.9 oz) with Vertical foregrip, Cutt Compensator

WEIGHT (LOADED) WITHOUT STOCK – 6.25 kg (13 lb 12.5 oz) loaded with 50-rd Type C Drum, Vertical forgrip, Cutts Compensator

WEIGHT (LOADED) WITH STOCK – 7.05 kg (15 lb 8.7 oz) loaded with 50-rd Type C Drum, Vertical forgrip, Cutts Compensator

STOCK WEIGHT – 0.80 kg (1 lb 12.2 oz)

SIGHTS –Fixed, Iron, Adjustable , Front, blade, rear Lyman folding ladder type sight with peep, Graduated from 0 to 549 m (650 yds) in 23 m (25 yd) increments, Battle sight square notch (ladder sight folded),  set to 46 m (50 yds),

EFFECTIVE RANGE – 182.9 m (200 yds)

OPERATION – Delayed blowback with Blish principle, fires from open bolt

TYPE OF FIRE – Selective, Semi and Full automatic

RATE OF FIRE – 50 rpm (Semi), 70 rpm (Full using 20 rd magazines),100 rpm (Full using 50 rd drums)

CYCLIC ROF – 600 – 700 rpm

FEED DEVICE – 20 (Type XX) round box magazine, Double column, double feed, 50 (Type C) round or 100 (Type L) round drum magazine

FEED DEVICE WEIGHT (EMPTY) – 20 rd 0.18 kg (6.4 oz), 50 rd drum 1.13 kg (2 lbs 7.8 oz), 100 rd drum 1.77 kg (3 lbs 14.4 oz)

FEED DEVICE WEIGHT (LOADED) – 20 rd 0.61 kg (1 lb 5.4 oz), 50 rd drum 2.21 kg (4 lbs 14 oz), 100 rd drum 3.92 kg (8 lbs 10 oz)

BASIC LOAD – Five Type XX 20-rd magazines, 2 Type L 50-rd drums (200 rounds)

LOAD WT – 7.52 kg (16 lb 9.3 oz)

MANUFACTURER – Savage Arms Company, Utica, NY, Auto-Ordnance Corporation, Bridgeport, Connecticut

STATUS – Obsolete

SERVICE – US Navy, Commercial (Military) sales to Sweden, Great Britain

     It is this configuration of Thompson that was originally sold to Great Britain and other allies. France fell before their order could be delivered and Norway received a good portion of their order. It was manufactured to US Navy specifications which required the cyclic rate of fire for the Model 1921 to be reduced. Adding weight to the bolt actuator lowered the cyclic rate to a speed more acceptable to the Navy. The first of the M1928 weapons to be produced were modified Colt M1921 models. To save time and cost, the “1” on the model number was overstamped with an “8.” This technique resulted in collectors referring to these models as Navy Overstamp specimens.