No great big "S" marked on the chamber, so she's still in original 8x50R.
BRASS for this number is easy: just open-out Boxer-primed 7.62x54R (Russian) casings to accept a .323" slug, trim to correct length (1.96 inches) and you should be away. I use a cheap Lee 8mm Lebel sizing die to push the shoulders back enough so they can chamber easily; you don't buy a lot of 8x50R die sets on the Old Age Pension! This works quite well; I am feeding an original Carbine and, soon, an 88/90.
Biggest PROBLEM you will encounter is that original ammo was loaded with a 244-grain slug and nobody appears to make that one any longer..... except possibly Ishapore, for domestic hunting use in India.
There ARE moulds for your own CAST bullets which are pretty close to that weight: 15 or 20 grains won't make much difference on this scale of things.
If you want your barrel to last almost forever without wear, read up on the Harris Universal Load for Military Rifles, see if you can profit from Harris's experience.
BTW, you will need a few Mannlicher clips for this rifle. It uses the same clip as comes with that "Nazi" 8x56R ammo, so not awfully hard to find. If you stick a piece of tape across the clip-ejection slot in your Magazine, it might look funny on the range but you won't lose or walk on any of your clips.
Nice toy! Do have fun!
