Currently I'm carrying a S&W 640-3 for my off-duty. I hear very good things about the Speer GD SB ammo, but trying to get it in my area in .38 or .357 is like snatching gold out of the air. Wally World seems to always have a few boxes of Winchester's PDX1 in .38+P. I'm sure it would be fine out of my GP100 with the 4 inch barrel, but wonder how it would perform out of the 640's 2 1/8 inch barrel. Anyone do any testing or have any links to articles/research on the PDX1 in .38+P out of short barrels? Thank you.