RV,
I haven't been loading 30-30, but I have been loading spitzers in a .357 Mag. After I figuered out my .223 Handi synthetic didn't like bullets loaded any longer than factory loads, I just started using the cannelure that is on the bullet for seating depth. Win white box .223 Varminters would shoot 1" groups at 100 yds, but those long reloads wouldn't come close to that.
BTW, the .357 with 200 gr Hornady spitzers will shoot 1 1/4" groups at 100 yards. When I finally get the forearm tension settled, it will probably do better than that.