Doesn't TSMG stand for Thompson Sub Machine Gun.aka, Tommy Gun....which was used in WW ll and chambered for 45ACP
Yes and no. The military TSMG's (M1928A1, M1 and M1A1) were all chambered for the 45 M1911, not anything described with an "ACP".
The War Department Basic Field Manual for the Thompson Submachine Gun, Caliber .45, M1928A1 (FM-40) of December 31, 1941 defines three cartridges authorized for use in the weapon; Ball Caliber .45, M1911, Tracer, Caliber .45 M1 and Dummy, Caliber .45, M1921.
Those folks blessed with a pre-WWII pistol chambered for the .45 ACP, and so marked on the barrel or slide, have every right to describe their as gun chambered for .45 ACP. All modern handguns and ammunition built by SAAMI members are marked 45 Auto. Look at the headstamp!
It is no more proper to refer to a cartridge by its obsolete designation than address someone's wife by her maiden name.
When you find yourself in a hole, it is best to stop digging.
Buff