Pre-1876 UMC 45 Colt Cartridge

Some comments on that round.

Bullet diameter. .455. If kept consistently with guns bored to match would have eliminated a lot of headaches for us who had later Smith 25-5 of various vintages. No crimp over ogive...interesting as noted above. And the hollow base... I assume it was to allow maximum obturation is guns of variable bore/groove dimensions? Thick skirt that's for sure. And, I think i remember Elmer Keith commenting that it also gave some additional volume for powder, which it would. Between that and balloon head cases, easy handling of the full-grown 40-grain black charge which you cite.

And look at that minimal rim. Surely sufficient for the Colt SAA w/ rod ejector but even in later SAAMI spec has caused some issues w/ swingout hand ejectors. I remember w/ my S&W 25-5's I couldn't mess around while ejecting empties or loaded rounds. You really need to work the ejector like you mean it with the muzzle pointed up or rounds may slip under the ejector star and sink back into the chamber. I remember reading that the 1909 Colt New Service and 09 service ammo possessed a wider rim which due to the smaller cylinder of the Colt SAA, would only allow 3 rounds of 09 ammo to be loaded in the SAA, skipping a chamber in between each due to the wider rim. I remember reading that 09 was loaded to higher pressure than the old stuff but I suspect the real reason for the wider rim was to preclude fall-back under the ejector star. Regardless, both rounds are powerful.

Anyway, very interesting and thanks for posting.