What do the revovlers actually say for caliber?
there are many different .45 calibers and not all are interchangeable , most in any way whatsoever
Calibers I own (or have owned)
.455 Colt (for the old Webley revovlers, narrow rim, will shoot in most .45 caliber rimmed revovlers, not the best choice though) this ammunition is stil available as factory ammunition.
.45 auto rim - a cartridge made for .45 revovlers that normally require half moon or full moon clips, to simplify loading, I haven't seen this ammunition in years
.45 auto, used in the 1917 revovler (among others) usually required half moon or full moon clips, this ammunition can be bought anywhere
.45 Schofield - antiquated cartridge making a comeback, you can shoot .455 in one of these revovlers, but only if th ecylinder has the clearance, Black Hills makes this ammunition for the cowboy shooters now, anemic loads but fun
.45 Colt (long colt to some) - longer Colt cartridge, will shoot the Schofield round as well, becoming much more common nowadays, this caliber has seen a recent resurrgence in popularity, if you have an older firearm make sure to use lighter laods, cowboy loads being a good start. DSome old pistols cannot handle the modern pressures
.454 Casull longer hihger pressure version of the .45 colt, snappy some would call it a "magnum" cartridge. Factory available, though you may have ot order it in, thumpy as hell.
.460 S&W longer than the Casull cartridge, still reverse compatible to calibers that will fire safely in a .45 colt. Factory ammunition available, but I doubt you inherited one of these, they are pretty damn new
there are others but these are the ones you are likely to come into contact with with any degree of likelihood.
So which do you want info and help on?