Cowboy .45 Special will work in any handgun ever chambered for .45 Colt or .45 S&W. it also happens to work very nicely in almost all handguns chambered for .45 ACP as well.
In rifles, there are three distinct choices.
Marlins require fairly extensive re-work, currently only being done by Spur spur45@macomb.com About fifteen such rifles currently exist, of which I own #s 1 and 2
It's a durn hillbilly assault rifle, Har!
The new carrier soon to be released (I just got my production prototypes for field demonstration and show and tell today, and as soon as we round up the carrier blanks we have on order and get the CNC work scheduled, a production run will commence) will make '66 and '73 rifles run with it also. The carrier ought to run as well as whatever ya got now, with no palpable difference, and allow use of lighter bullets with decent accuracy. A '60 Henry version will follow shortly thereafter.
I am told that at least some winchester '94AEs chambered in .45 colt will run the cartridge just as they are. I have not tried it, but I have a report that one feller tried it and lo and behind they fed flawlessly. Not that I'd suggest a 94AE as a "gamer rifle", but if ya got one and like it.....
The short case severely reduced case capacity and RAISES pressures (just like .45 ACP VS Long Colt) so at modest levels with light bullets we still get enough pressure for a decent burn. I have successfully shot bullets as heavy as 318 grains, and as light as 120 grains with the short cases.