A little more data. I just bought my first Pietta, a 5-year-old Cimarron Frontier. First thing I did was pull the base pin from a early 3rd Gen Colt and try it in the Pietta. Fit fine. Inserting it just through the cylinder and wiggling side to side showed it to be a tad tighter than the Pietta pin. Fit the gun fine, but I noticed there is a bit of fore/aft play because the groove on the base pin is wider than the narrow Pietta groove, but I would not expect a problem with that, at least not with the loads I'm shooting. I'll be posting about this revolver in another thread.