your new cast 30-30 slug at .860 is much shorter than the Hornady 140s at 1.203, so it should leave plenty of roon in any 30wcf case for powder, mebbe enuff powder to get 3000fps!?!?!?!?!

I'm also sure that, at 3000 fps, we could probably throw those bullets more accurately than they would shoot! Probably even left-handed! (and if you've ever seen me throw anything left-handed, you know how bad that would be).