Luger problem

[Lugerdoc]

During WW2 Mauser increased the strength of the PO8 recoil spring from 19 turns to 21, so that use of the hotter WW2 SMG ammo would not damage the pistol. This is probably the root of the "hot ammo" myth. The problem with rebuilt, reblued shooters, you don't know if a proper recoil (and other) spring has been installed, so even with a new MG mag, it's a matter of trial & error as to what ammo works best. TH