I just picked up a slug of 45 Auto Rim cases... can run those through the 45 Colt chambers if you want... been planning on having my machinist buddy make me an ACP cylinder for my snubbie, just to have the option... but I do shoot CASS, & have a pair of regualr Montados in 45 Colt, as well as a lever gun in that chambering... along with 1000 cases I reload... as mentioned earlier, the 45 Colt is an easy reload... as good a cartridge as any to start with, & plenty cheap to reload... as far as reduced loads on that bigger case... ( or the acp for that matter ) Trailboss can be your friend... CASS "gamer" shooters have been loading mouse phart loads in that cartridge for a long time... I personally use it to load mid range loads when I shoot CASS
BTW... if you do choose the 45 Colt, you can shoot those Auto Rims, as well as 45 Schofield cases... & you are head spacing on the rims... if you getting the shorter 45 acp chambers, you are headspacing on the case mouth ( makes brass length more critical for proper function ) than the longer chambers headspacing on the rims... I have several revolvers that head space on the case mouth, & it's not really an issue, just something else that can go wrong