I have some old 9MM 15 shot Pro Mags for a Sig P228 that are jamomatics or wouldn't lock the slide back (I bought them just before the Clinton gun ban fiasco, and they were all that were left on the open market).

Fast forward to 2018, when I bought a Bersa Pro Thunder Compact 9MM just to try it out. Love the gun, but wasn't fond of the pinkie rest magazine floor plate.

So I swapped out the floor plates and just like that, flat mags for my Bersa.