You are correct, the 45 is a MP copy of the RCBS SAA. It is a heavy bullet designed by Dave Scovill if memory serves for the Colt SAA. I sent him several of these sized .454" years ago for an article in Handloader Magazine. And while there are other bullets that may claim best overall bullet for the 45 Colt, I believe this one is good as any. And at risk of speaking for Mr. Keith, I believe he would approve.