Dawg,
On the old Leverguns site, Jim Taylor said he and Paco Kelly shot “thousands” of rounds in the FA 454 using .45 Colt cases. This was before 454 brass was readily available and was really expensive (I’ve still got some old FA cases that I paid $50 for a box of 50 unprimed brass – mid 80s). Jim Taylor said he used a belled case to scrape the carbon/lead buildup from the chambers. I think he mentioned filing some teeth in the mouth of the belled case. I’ve had good luck with a .45 cal bronze brush wrapped with medium bronze wool, chucked in an electric drill. Just make sure you get all the buildup removed.
I’ve also crimped cast SWCs over the front drive band in .454 cases with excellent results. I’ve only done this with loads in the 900 to 1,100 fps range. One of the most accurate loads in my .454 was using a 270gr SAA sized at .454, crimped over the front drive band, driven at about 950 fps using HP38.