Lloyd, that 260 @ 1000fps sounds like a 20,000psi load, at least from Brian Pearce's article"Understanding the .45 Colt", in Handloader, June 2002. OK, Thanx. And RedHawk, I'm concerned about the material thickness between the chamber wall & the o. d. of the cylinder in the .45 Colt chambering. I will call S&W, & thanx to you, too. JD45