Similar bullet diameters are found in the 9mm luger, 9mm largo, .357 magnum, 38 automatic, 38 super automatic, 38 Smith & Wesson (which is the largest bullet diameter at .360), and a few rare old cowboy and BP guns.
None of these have an actual .380 bore, most are .355, .357, or .360.
Now, explain +P loads. ;>)
/john