Originally Posted by Ranger-6
I was able to shoot 9mm out of the .380, but was not able to shoot .380 out of the 9mm. The head-space was about 1/16 inch too short. But, I did try.
Shouldn't that be vise versa? If 9 mm fits in a .380, that strikes me as a dangerous overpressure situation if fired, aside from the 9 mm being longer.
As for the 9x18, it shouldn't fit in either of the others. If it does, don't pull the trigger. 9x18 bullet diameter is .363", 9mm Luger & 9 mm Kurtz (.380 acp) typically run .355" or .356". Pressures could get exciting.
Max pressure for:
.380 ACP - 21,500 psi.
9 mm Makarov - 23,200 psi
9 mm Luger - 35,000 psi (or 38,500 +p)
.380 can be made to fire in a 9 mm Luger, though it's headspacing on the extractor. Probably not dangerous but not a great idea. In a Mak, the situation is probably similar, though the slop in the bore will eradicate anything resembling accuracy.
Even if you can "make it fit," don't mix & match your different calibers.