I’m still not convinced that there is anything special about these cartridges. A few years ago I rounded up a bunch of my 45 cartridges, both Colt and S&W, and made measurements. The only difference I could see in the REM-UMC 45 COLT was that the rim diameter was slightly smaller (.509") than older BP S&W cartridges (.515"). That’s only .006", hardly enough to be notable. It’s true that this brought the rim diameter more into line with the old BP 45 Colt cartridges (.506") but I also found many modern 45 COLT cases that had rim diameters that were larger (.510").
As Dave said, I don’t think the larger rim of the 45 S&W cartridges made them unsuitable for use in the Colt revolvers such as was implied in COTW. Quite a few 45 S&W cartridges were fired at the Battle of the Little Bighorn and they seemed to work just fine in the Colt revolvers. In fact, the Cavalry was later issued 45 S&W on a regular basis so that troopers armed with either revolver would have workable ammunition without having the supply problems associated with two cartridges. It was not long before the long cartridges were phased out as standard issue.
Maybe there is a real reason for the REM-UMC 45 COLT cartridges but I think it may have been more imagined than real. Or, it may be that someone noticed the difference in the rim diameters and jumped to the conclusion that there must be a reason for it. It’s always nice to come up with a reason for something, even when one isn’t called for.
Calling them 45 COLT GOVERNMENT is just fine with me. But I don’t think we should assume it means anything other than a name that Remington may have attached to it. After all, there are many other cartridges with the moniker “Government” attached to them and it’s mostly for sales purposes.
As Dave said, a box sure would help. Until then, color me skeptical.