I had a shooting buddy of mine, who shoots a LOT of C&B advise me to forget a .45 Colt conversion, if I wanted my opentop design Uberti 1860 Army to have a long, useful life. He said the gun will eventually shoot loose, even with BP & round ball. With the cartridge load & a 250gr bullet, (even the so-called mousefart "cowboy" loads will stress the gun much harder) with a lot more frequent firing due to the faster reloading, this will happen much quicker. That was his advice to me & I pass it along to you. The ROAs & Rem. 1858s might be able to handle it, but not the OTs. Of course, it's your decision, jd45