Started loading .30-30 cast bullet loads about 40 years ago. Both of my kids grew up with Winchester Model 94's, now all of my grandkids have them as well (cleaned me out, as a matter of fact). Still loading all the fired brass all the kids send to me every year (don't think they have ever learned that .30-30 ammo can be bought at any well stocked retail store). I use the Lee C309-170F mold, cast with 50% wheel weights and 50% Linotype metal, Hornady crimp-on gas checks, sized .309" with NRA formula Alox lube, 30 grains H-335 and standard primers. That load has filled freezers with venison going on 3 generations now (nine grandkids, 3 great-grandkids, all well fed).
Them grandkids sure have a good grandpa!
And just so it is mentioned, no pointed bullets that might set off the primers of the rounds in the magazine tube...
Cast bullet diameter is no more important and possibly less important than nose diameter. Gas checked bullets sized to 0.001" or 0.002" over groove diameter combined with a nose that had a cylindrical portion that fit snugly in the lands usually gave me the best accuracy. A bore riding nose is a basic feature for shooting tight groups with cast rifle bullets.
Bear in mind that bullets that in theory should group great do not always do so. It always comes down to testing different combinations in a particular rifle.
about 310 and if I may suggest a powder for lead it would be H4198
That was one of the tricks used by deer hunters who reloaded .30-30 using spitzer bullets and a M94 or Marlin. One cartridge in the chamber and one in the magazine. If you couldn't get a deer with two shots, then you probably couldn't with 20.
One way to address that is to use 130 grain spitzers that are designed for lighter game. In addition to their thinner jackets you can boost their velocity. Also their shorter noses fit the Remington's box magazine better.[...] Not all [spitzer] bullets will reliably expand at the lower velocities associated with the 30-30. Most bullets used for a 30-30 are specifically designed to expand at those lower velocities so take care when choosing your hunting bullets.