Some technical notes:

1. .38 Super +P in a .38 Special is *not* listed in the "Unsafe Combinations" Data Sheet at SAMMI. Of course there's a lot of things I could come up with that also aren't on that sheet. They only list .380 and .357 as an unsafe combination in the .38 Special.

2. All .38 Super ammo is +P. SAMMI has no designation for .38 Super without the +P affixed. Some years ago they did this to try and further differentiate it from the parent .38 ACP which of course has an identical case.

There's a bunch of obsolete European 9mm's out there that could theoretically chamber a .38 Super if their chamber/extractor was sloppy enough. I'm talking about 9mm Largo, 9mm Steyr. These are the guns the ammo manufacturers were worried about the .38 Super finding it's way into.