Re: posts by mbnatt & LoboGunLeather:
Lobo's post, while accurate & informative, didn't exactly address mbnatt's question regarding .38 Colt and .38 S&W. It is correct that the .38 Long Colt was our U.S. Service cartridge for several years, and that the .38 Smith & Wesson Special was based on it, but with a longer case. The .38 Colt New Police, however, IS identical to the .38 S&W, including the larger diameter case and same bullet weight, albeit with a flat point. Both the Short Colt and Long Colt can be fired without difficulty in any revolver chambered to .38 Special, but both the .38 S&W and Colt NP are parallels of the .380 MkII (and Mk I as well, I surmise), and will seldom chamber in a .38 Spl.
Hope this helps.

Larry