You can probably spend several weeks, months or even years researching that debate!
If you keep the velo under 1450ish you can shoot wheelweight (unquenched), or softer, plain base bullets in them just fine. The trick is fitting the bullet to the throat (ie, not trying to use too small a dia. bullet, regardless of alloy).
If you want to go faster use quenched WWt or lino alloy, etc.
You might want to check out the Cast Bullet Forum here on GBO.