45 Colt chambers, particularly the old ones are larger because of the historical use of cast bullets primarily. Not too much for the FA's I have seen.
We are talking about working the brass over several resizing's. You take a case that was designed for very low pressures. Look at the schematics of 45 Long Colt and compare those to the magnum cases. Big difference in case and web thickness.Then you fire it in loose chambers. Then you resize. Over and over. Hot loads are one thing, but 454 loads are much hotter. (you were talking about equal performance). I load conservative, on my magnum cases, most of the time it is a failure of the case mouth that occurs first with using minimum crimp practices. With the 45 Colt you get internal stress cracks right above the web section first, loading at magnum pressures. As little as 2-3 reloads sometimes. Depending on the gun.* If you have not experienced this, you have not done it. Period.
Look at any reputable loading manual, you will see the warnings.
45 Colt at magnum pressures is one thing. At 454 pressures is a whole different ball game. You wanted equal performance.
Crimping in a lubrication groove is done. Matching the correct bullet to do that is the key. This limits your options. Eliminates the use of Jacketed bullets also. Why not use the correct case? A safer case. If you have spent the money on a nice FA revolver, surely buying 454 brass is not an issue. THEY WILL LAST LONGER!
Be safe my friend.
* There is one advantage to using a good ultrasonic cleaner. You can see these stress points much easier.
