I can't see why anyone would use, or try to use, shot cartridges in a Thompson.
First, the shot is very small, on the order of No. 6. In dense jungle cover it would be virtually useless past a few feet, if that. It would be a worse choice than straight ball ammo. Even shotguns loaded with buckshot had limited range in the jungle due to the heavy leaf and brush canopy, but within that range gave better chance of a hit with less chance of the brush deflecting the projectile.
Second, they will not function the action of either a 1911 or a Thompson -- in neither gun will the rounds, upon firing, eject or cycle the action enough to pick up a new round out of the magazine. In other words, there's no ripping off a magazine or two of these shot cartridges unless the firer does so manually.
Third, feeding these rounds through a magazine is, at best, an iffy proposition. They were designed to be single loaded into the 1911. Survival kits contained a box with, IIRC, 12 rounds of ball and 12 rounds of shot ammo.
CCI's .45 ACP shotshells are very close to the military shotshells of WW II, both dimensionally and ballistically.
There was a shot cartridge developed for the Thompson for use in riot control prior to World War II, IIRC, the early 1930s. However, this was not the basis for the military's shot cartridges during the War. Shot size and power was quite a bit different, and there's no indication that these cartridges were ever considered for distribution during the war. In fact, I'm fairly certain that they had been out of production for a number of years by the time the US entered the War.
OK, Phil Sharpe says Peters developed the riot cartridge for the Thompson in about 1922.
