FWIW, S&W chose the .38 Long Colt as the base for the .38 Special because the .38 Long Colt was then (1899) the U.S. service cartridge and S&W decided that having its new M&P revolver capable of using that common cartridge was worth swallowing a little pride. There was a lot of dissatisfaction in the military with the issue Colt .38 revolver, and S&W hoped that its new revolver and more powerful cartridge would get it a military contract. Early S&W M&P's were even marked for .38 Special and U.S. Service Cartridges (they didn't call it ".38 Long Colt", of course).