I would buy three powders in your case. A container of Rel 15, Varget, IMR 4350. If I had to pick just one and your main gun was the 270, and all you wanted was on powder to start, IMR 4350 would be good, as it would give satisfactory results with your 7.08 and your 30-06 too. (H4831, IMR4831, H1000, Rel 22, Rel 19 will give better external ballistics for your 270, but not neccesarily better accuracy. Buy as many as you can afford and load as many as you can. It just gets better and better.).