You should be safe using 9.3x57 starting loads for like weight bullets. You can probably use .358 cal bullets with starting loads as well without damaging anything. Not unlike a tight bore (.3065") Palma rifle using .308 bullets. Lead bullets open up another arena. I would suggest playing with H4895. It works great in my 9.3x57 and takes to reduced loads very well. IMR 3031 should work well too. All my data is at home but you should be able google up some 9.3 data.
Lube your necks inside very well and run them through the die, should size up no problemo.
