A special cartridge called the Remington-Thompson Model 1923 was developed and used the XVIII (18 rd magazine) which was also used for the Peters- Thompson shot cartridge and is not the same as the 45 ACP shot cartridge.
The Thompson Model 1923 cartridge was chambered in a 14 1/2 inch barrel that also had a bipod. The muzzle velocity was 1450 fps with a 250 gr bullet. It was discontinued shortly after introduction in 1923 but the XVIII magazine continued in service with the Peters-Thompson shot cartridge. The 45 Thompson Model 1923 cartridge case is 1/8 inch longer than the 45 ACP cartridge caseAttachment 68499
cartridges in photo: 9.8 Colt ACP, 45 Thompson Model 1923 and 455 Webley auto