In the World of Classic SMGs; The Thompson Reigns Supreme

The infamous 'Tommy Gun' of the 1920's has earned it's place as an American icon.

January 13, 2026 By Will Dabbs, MD

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John Taliaferro Thompson was one seriously busy guy. He served 33 years in uniform. At the time of his promotion, Thompson was the youngest full Colonel in the US Army. While he was responsible for the adoption of the .45ACP cartridge, the M1911 pistol, and the M1903 Springfield rifle, it was a certain radically advanced submachine gun that ensured his place in history as a small arms legend.

The M1921 Thompson submachine gun was lyrically complicated. However, coming as it did at the very end of WWI, the gun was also unique for its era. The first prototypes came available the day after the First World War ended. Not unlike Gene Stoner and his Armalite buddies who designed the M16, General Thompson’s Auto-Ordnance Company was a think tank. They designed the SMG that bore the great man’s name, but they lacked the means to produce it. That first block of 15,000 guns was farmed out to Colt’s Manufacturing.

Those original Colt Thompsons were simply magnificent contrivances. Meticulously cut out of big blocks of forged steel and then beautifully blued, they were archetypal examples of the interwar gunmaker’s art. However, with no wars left to fight, there were relatively few buyers. The basic gun was expensive at $175. Adding the distinctive Cutts compensator boosted the price up to $200. That’s around $3,600 today. Auto-Ordnance was in trouble.

The M1921 Thompson saw enough use during the gangster wars to scare people. Having the Tommy Gun luridly splashed across the Saturday afternoon newsreels helped pass the 1934 National Firearms Act that taxed machineguns out of existence. The examples that survived command crazy prices nowadays.

Mechanical Details

Blish lock of the Thompson Machine gun — The Blish lock (the bronze bit shown here) was an inspired yet ultimately unnecessary addition to the Thompson SMG action. (Photo provided by author.)

The beating heart of those early Thompsons was the Blish lock. First postulated by American inventor John Bell Blish, the Blish lock operated on the theory that two dissimilar metals, in this case steel and bronze, would exhibit different coefficients of sliding friction based upon the pressure they were under. These early guns incorporated a curious H-shaped bronze locking piece as part of the mechanism. It was expensive and difficult to produce. The Blish lock was also superfluous. British troops fighting in North Africa sometimes ground the legs off of the Blish lock to enhance the gun’s reliability in the dusty desert environment. The modified guns ran just fine.

Early M1921 Thompsons cycled at around 900 rpm. Auto-Ordnance redesigned the gun to include a heavier bolt actuator and stiffer recoil spring to slow the rate of fire down to around 700 rpm. This earned the gun a new M1928 designation. Aside from these parts, the two models were identical. M1928 Thompsons came from that same first run of 15,000 weapons. They had the “1” overstamped with an “8” to designate the change.

Drum magazine on Thompson M1921 — It’s a bit risky to shoot these M1921 Thompsons with their original parts. Period-correct vintage replacement components seldom if ever come to market. (Photo provided by author.)

The Thompson was hopelessly obsolete by WWII, but it was the only gun of its type available. The British bought all of them they could get their hands on. These early weapons were tweaked slightly and designated the M1928A1.

The M1921 and M1928 had finned barrels, removable buttstocks, and top-mounted bolt actuators. They were also cut to accept drum magazines. However, they were really complicated to manufacture. As a result, the Ordnance Department commissioned a redesign in 1942.

The subsequent M1 Thompson was a very different beast. The Blish lock was gone as were the cooling fins on the barrel. They deleted the Cutts compensator and did away with the drum mounting slots. Along the way, the charging handle was simplified and moved to the right side of the receiver. M1928A1 guns could be found with either vertical or horizontal foregrips. Those of the M1 were all horizontal. The M1 Thompson used a bolt with a separate pivoting firing pin. That of the M1A1 was fixed in the bolt face. These guns were otherwise identical.

Types of Thompsons

Colt M1921, GI M1928A1 and M1A1 — From top to bottom, we have the M1921 Colt Thompson, the G.I. M1928A1, and the simplified M1A1. (Photo provided by author.)

Now fast forward to the Information Age, and transferable Thompsons fractionate down into several broad categories. As with any collectible firearm, the details regarding provenance, condition, and originality drive the price. Some great books have been written on this subject.

Original unaltered M1921 Colt Thompsons are the most desirable and most expensive. M1928 overstamps are right behind them. Wartime M1928A1 examples are a bit cheaper. Government-surplus M1 and M1A1 Tommies are the cheapest of the original Curio and Relic (C&R) sort, though they still cost a holy fortune. Thompsons all sport index marks on the barrels, so it is an easy thing to tell if a barrel has been replaced. Collectors live or die over the zillion little details.

M1928 compared to M1921 — (Top Image) The West Hurley M1928 Thompsons are mechanically identical to the earlier models. (Photo provided by Rock Island Auctions.) (Bottom image) The original Colt M1921 Thompson is a thing of mechanical beauty. It is the ultimate collectible machine gun. (Photo provided by author.)

WWII saved the Auto-Ordnance Corporation, but not before it had changed hands a time or two. By the 1950’s, the company was in dire straits and sold to George Numrich (of Numrich Gun Parts fame). Numrich found himself in possession of the Thompson name and a “zillion” G.I.-surplus parts. He therefore began producing new receivers in West Hurley, New York, in the mid-1960’s. Most of these guns were M1928 models, though there were a few M1A1’s as well. There were even 300 .22LR versions built on standard M1928 receivers. All of these Thompsons were nicely blued. They also had “West Hurley, New York” stamped on the right side of the receivers. Auto-Ordnance also made new closed-bolt semi-auto versions starting in the 1970s, and those are still available via Kahr-Arms.com.

In the past, West Hurley guns were considered the “mutts” of the Thompson world because of their miscellaneous parts. Additionally, there were some quality control issues that adversely affected reliability. This far out, however, most all West Hurley guns should have been tweaked such that they run well. Relative rarity has made all transferable Thompsons expensive regardless of their origins.

Roll mark on Thompson SMG — Like any other collectible firearm only more so, the markings on the side of the gun drive the price. (Photo provided by author.)

Prices

According to MachineGunPrice Guide.com, original M1921 Colt Thompsons are running $55,000–$60,000 today. M1928 overstamps are about the same. M1 and M1A1 C&R guns hover around $35k.

Charging handle on Thompson — The charging handle on the M1A1 Thompson was a simple peg oriented on the right side of the gun. (Photo provided by author.)

West Hurley M1928’s are moving for around $23,000. West Hurley M1s and M1928 .22s are so rare it is tough to establish a reliable price. I would expect the M1928 .22 to cost about what a standard West Hurley M1928 might. It is theoretically possible to convert a .22 version back to fire .45, but it would be a butt whooping. You’d have to gut the gun and replace the barrel as well as the internals. There is also the issue with the paperwork listing the weapon as chambered in .22. As a result, swapping an M1928 .22 back to its centerfire caliber is likely just not worth
the trouble.

There were also some full-auto Thompson conversions of semi-autos before May 19, 1986. However, these will not accept many original internal parts (like the bolt) as the BATF required the receivers to be made “taller” so that original full-auto parts could not just be dropped in.

Ruminations

Stamp on Colt SMG — Colt spared no effort or expense in making that first run of 15,000 Thompson submachine guns. They were uniformly gorgeous. (Photo provided by author.)

Original Colt M1921 parts are readily identifiable and essentially irreplaceable. As a result, it gets riskier shooting these old original guns as time goes on. Most folks who want to run their vintage M1921 Thompsons will replace the bolt and actuator with surplus GI parts, which are still available at relatively reasonable prices. That way if something breaks, it’s not the end of the world.

All Thompsons are heavy, awkward, and fairly clumsy. However, cycling an original by hand is like manipulating a sewing machine. They are also great fun to shoot. Additionally, the historical gravitas that is inextricably attached to the Thompson makes it reliably desirable. As a result, original Thompson submachine guns will forever be the crown jewel in the advanced machinegun collector’s crown.