7-08, IMR 4350 is one of the best powders for the .30-06. I have found that the bullet weight and shape being matched to the particular rifle is more important than the powder choice, as long as the powder is a traditional or proven choice for the caliber. Since you have tried many different styles and weight of bullets, I agree with some of the other guys here, your rifle may need some tuning. It could be your scope or a variety of minor ills but you should have gotten some type of accuracy with all the loads you have tried.
