G4F, that (EDM rifling) is what I was thinking of. Didn't know about the 6 grooves on the 25-2's. Thanks for that little bit of info!

The barrel in AKtinman's post above looks like it has 6, and my 3 .45 Colt 625's all have 5, so there definitely appears to be a difference between LC and ACP.

I will say that my 2 post-'94 Mountain Guns (-6 and -7) definitely look like they have shallower rifling than my 625-5 Classic, but all 3 shoot plain-based wheelweight bullets (RCBS 270SAA mould) really well on top of an appropriate charge of 2400.

I wonder if some of the inaccuracy and leading folks experience with lead in .45acp could be traced to using bevel-based designs and/or .451" diameter bullets.