Alloy (and any hardness treatment) should match the chamber pressure of your load.
Velocity matters, for stabilization and lubrication.
Your load makes a ton of difference.
Bullet diameter is often best with body one-thousandths over groove diameter and nose close to bore diameter (especially important with a long nose in a bore-riding bullet).
And you don't tell us much about these important characteristics. So, every thing here is really a wild guess.
A moderately fast rifle powder with a hardened wheel weight bullet (16-20 Brinnell hardness) that is heavy for caliber (compared to jacketed) loaded to around 1900 FPS is where I start with most of my mil-surps, including 1903 Springfield and several 8mm Mauser 98 designs.
good luck, garrisonjoe