Right hand twist.

[Dave]

Very interesting, thanks guys. I have one of those Rem.-UMC 45 thompson cartriges. The bullet has more of a tapper to the end rather ten the round bullet on the regular .45 ACP. It can be seen in the picture above, by RCS.

[Jim K]

The M1923 TSMG for the .45 R-T cartridge used the longer (front to rear) box magazine previously developed for the shot cartridge. While the same top to bottom length as the Type XX (20 round) magazine, the recommendation was to load it to only 18 rounds of shot cartridges to prevent the spring tension from crushing the paper shot containers of the shotshells. Those magazines are marked "for shot cartridges" or "for 18 shot cartridges." I have never seen them referred to as Type XVIII, but it would certainly be in line with the designation of other magazines.

The magazines made for the .45 R-T round are the same as for the shot magazine, but do not have any marking on them.

Neither the shot cartridge nor the .45 R-T round will fit in the drum magazines. The guns will work with the special box magazines because the standard box mag does not entirely fill the magazine space as the drums do, so a slightly longer (front to rear) box mag will fit. The use of shot cartridges was reportedly unreliable, though they would function the gun.

(Much of the above and in my other posts was obtained from "Thompson: the American Legend" by Tracie Hill, plus my own knowledge of the guns from owning and firing them.)

Jim