The particular guns throat is going to figgure highly in what maximum velocity will be, but with LBT bullets I always put a strong drive band up front, which stands a pretty vicious jump to rifling. Consider the jump in revolvers, which is HUGE compared to rifles, and they can deliver 1 inch accuracy at 100 yards.
Use the largest diameter that will chamber when seated to max length for your magazine, coupled with the slowest ball powders that would be used for jacketed, and work up till accuracy goes out the window. You should be able to find a load that's near max jacketed 08 speed which shoots with good accuracy.
I forgot to mention. I have two 30-06 rifles. One a tight new barrel, the other an old rebarreled Springfield, with very worn throat, as I recall about .314 at the beginning and LONG, so that the tight barrel ammo has to jump over 5/8 of an inch. The worn gun shoots best with ammo fitted to it, of coarse but with target loads It will shoot the tight barrel ammo into 5/8 inch at 100 yards, and with stout loads, which I limit to 2400 fps to keep meat destruction under control, it gives excellent hunting accuracy for big game.
You will not be dealing with a jump anywhere near this illustration.
