You'll find the the actual rifling, the forcing cone, and the end of the chamber, varies greatly in the 45 Colt chamberings, from gun to gun and brand to brand.
The chamber mouth on most all of the cylinders is too big, leading to shaving of bullets and leading at the entrance of the barrel, in the gap between the cylinder and the barrel.
The Freedom Arms (454 Casull) revolvers are the only ones done "properly". Those have the tight .451-.452 chamber mouths instead of the more common Ruger .454-.455, also found on the various generations of Colt SAA revolvers and the mulitude of replicas thereof. Also the Freedom Arms revolvers are align bored with the cylinder placed in the frame, so that cylinder to barrel alignment is perfect, or at least as perfect as humans and CNC equipment can make them. That's why the Freedom Arms revolvers cost near $2K.
SOME of the problem can be cured, by getting a tool from Brownell's to put an 11 degree chamfer on the back of the barrel. A REALLY good gunsmith can also take a longer barrel, cut it, rethread it, and cut a new forcing cone, preferrable a Taylor forcing cone, like Freedom Arms uses, and increase both accuracy AND velocity, along with virtually eliminating leading and bullet shaving. The longer but smoother transition to the rifling is the key.
You can have a Ruger single action done like the Freedom Arms revolvers are, Hamilton Bowen in LouisvilleTN and John Linebaugh in Cody Wyoming make some real beauties. More known for the .475 and .500 Magnum conversions, both do incredible work on Rugers, and on some Colt SAA's. But you end up with as much invested as a Freedom Arms would cost.
