Have you checked your bore diameter? I thought the Austrian "8mm" was considerably wider than the "8mm" for Mausers. IIRC Graf & Sons sells special bullets and brass for this. Regular 8mm bullets may be too narrow to engage.
"Know that the pistol has no value, we practically don't use it. We need grenades, rifles, machine guns, and explosives."
Mordechai Anielewicz, April 23, 1943