Talk about technical, out of my eleven 9mils and 380s, less than half of the barrels mic'd to .355". Most require .356" bullets, and some require .357"-.358". Oddly enough my two 38 Sups are right at .355".Technically no, .38 super is .356 dia. That said some of the barrel manufacturers have gone to .355 dia. on the super barrels.