Xxero. You are correct in saying lead alloy bullets are harded than pure lead. However, it has been proven that more than two percent of tin does nothing more than waste expensive tin. Antimony is what makes lead bullets hard. Arsenic, up to 0.05 percent will make lead alloys even harder. Straight wheel weights have enough antinony to make a bullet of 12 to 13 BHN. (Brinnell Hardness Number)Add some linotype to the wheel weights, or some 50/50 bar solder, ot leadless solder to slightly increase the percentage of tin, and you have one very castable alloy. If you then heat treat the cast bullet, you can, depending on the amount of antimony in the mix) have a bullet as hard as 32 BHN, although somewhere between 28 and 30 BHN is more the norm.
This is more than hard enough to reduce the chance of stripping lead from the bullet. With load adjustment, you can have the bullet hit to point of aim at say 50 yards, without readjusting your normal scope setting. A load somewhere between 1500 and 1800 FPS makes a great small game and grouse load, without too loud a report while big game hunting. It can also be used as a finishing shot on game you've shot and is not quite dead.
I have done this with .308 Win. and 30-06 for years. Just haven't gotten around to working one up with the .300 Mag. yet.
BTW. Full power 30-30 loads are no problem whatsoever.