[ignats]

The original name given by Colt when the cartridge first came out was 38 ACP that was back in the early 1900's for Colt Models 1900 and 1902. During 1927 Colt came out with the COLT SUPER .38 AUTOMATIC which is a higher pressure and velocity version of the same older cartridge. The pistol used the same frame as the Colt Government Model that is chambered in .45 ACP. The slide is different. Colts did this as measure to prevent people from loading the new cartridge into older .38 ACP pistols and by putting the SUPER out front I suppose they were trying to warn the public.

The older pistols were roll marked as previously stated however somewhere along the line, the name morphed to .38 SUPER. This may have been as a result of other companies copying Colt. You will find the same thing with .44-40 and .38-40. Winchester named them 44 WCF and 38 WCF (Winchester Center Fire). Other companies i.e. Marlin started calling it .44-40 rather than use Winchester's name or abbreviation. on their product.

So, to answer your question I'm just used to the using the original name.

BTW, most of the factory ammo is now marked .38 SUPER +P so as not to confuse it with the older .38 ACP. It is perfectly safe to use in modern pistols designed for Super 38 or 38 Super BUT NOT the older 38 ACP.