Anybody familiar with a Steyr 8x56?

The 8x56 Mannlicher-Schoenauer is a clic hunting cartridge, but if it's a military rifle, I suspect what you saw was a Hungarian M31 or one of its variants, which is yet another different cartridge, being rimmed where the M-S is rimless. So be especially careful before you buy and try to feed it the wrong 8x56 cartridge! The Hungarian is also .329 caliber, so even handloading may be more of a challenge than you anticipate.