The old Python had a tapered bore something like .001-.002 forcing cone to muzzle. Colt tooted this as having a better grip/seal on the bullet. They also pushed a "mystery metal" ball down each barrel bore to burnish it and smooth it. That said all the old Colt craftsmen are gone. Nobody or nearly nobody out in the real world can work on the old ones. That said I like the new one. Don't know if I'll ever afford one. I have an old one from 1980 from the custom shop. Mine was $468.00(NIB).........But that was 40 years ago.