No doubt Preservefreedom is correct in surmising changes to metal treatment, etc. Smith and Wesson incorporated changes to the J-frame first developed to create the .357 j-frames into all versions, including the airweight .38s. I think the biggest single factor in Smith announcing that J-frames were rated for plus P use was the fact that Taurus announced it first for their line of small-framed revolvers. Some design changes, lots of marketing changes. The marketing folks trumped the bean counters. I used to have a 642-1 purchased prior to any plus P ratings. After the announcement I called Smith and was told that if it was a -1 then it was, indeed, rated for plus P. It was not marketed that way until after the Taurus marketing campaign. It did incorporate some changes over prior 642s such as, I believe, slightly thicker top strap, radius cylinder window corners, etc. Laz
