Those Mysterious Forty-fives

[sheepherder]

Originally Posted by John Sabato

Isn't the .38 Super considered Semi-Rimmed, and actually headspaces on the "rim"? At least that is what I THINK I remember... and .38 ACP was "rimless" like most of the auto pistol cartridges, as I recall...

They are exactly the same case, only difference is the load. The case head is .405" while the body is .385", so it is a semi-rimmed cartridge.

The Colt's Government Model 38 Super Auto barrel, like the 45 ACP barrel, does not have any support for the case head/rim. It headspaces on the case mouth, like the 9mm Parabellum.

Pics attached. In the two top views, the cartridge is pushed into the chamber against the case mouth. In the bottom view, the extractor is holding the cartridge against the breech face. You can compare the views to see how much difference there is.

And the .45ACP also headspaces on the case mouth, not the rim.