The Thompson M1926 was a submachine gun designed and manufactured at Birmingham Small Arms.
In 1923, Auto Ordnance entered their Thompson M1923 for French and Belgian military trials. While the French were quite unimpressed with the weapon, the Belgians liked it, but felt it should be chambered for 9x19mm Parabellum instead of .45 ACP, since 9mm ammunition was much more popular in Europe. Auto Ordnance did not have the manufacturing facilities to produce 9mm Thompsons, but they were rather desperate for a European purchase of their weapon, so they contacted Birmingham Small Arms in England to create licensed "European models". The result was the so-called M1926, which differed from the original Thompson not only internally but externally too. The rate of fire was increased from 800 rounds per minute to 1200 rounds per minute. A major problem with this, however, was that the M1926 only accepted 20-round stick magazines, not drums, so the blistering rate of fire quickly depleted the ammunition in each mag. The M1926 was entered into French and Belgian military trials, with little success. The French trials noted that:
"The Thompson submachine gun discharges in single fire or as a machine gun. In the first case, precision is excellent up to 600 metres; in the second the overly rapid fire does not allow the weapon to be shot unsupported without excessive scattering. The weapon underwent a test fire of 3,500 rounds with 2,500 in automatic fire, which led to only a few minor problems, but inspection revealed a broken bolt and galling on the Blish lock, on the cocking notch and on the tip of the sear."
Ultimately, the weapon's failure came down to the fact that it had an almost uncontrollable rate of fire during automatic firing, while it performed less adequately than a rifle in single-shot mode. The M1926 was seen to be a failure, until in 1929 Birmingham Small Arms upgraded the weapon as the M1929. It was given a pistol grip to improve the weapon's stability, the magazine was curved and the stock was upgraded. However, this did little to interest new buyers, and manufacture of Thompson submachine guns at BSA ceased in 1930.