H4350 is at the slow end for 150 grainers, true, but I just used it to load up some 125 gr bullets in my 30-06 (for fun) and I had two groups (non-consecutive) in my ladder around MOA (4 shots 100y). While you might get ultimately better accuracy with another powder, H4350 is just fine. If you have it, go ahead and try it. If you haven't bought any yet -which given that you are just starting is likely - grab a few different powders and a few different bullets (brands and weights) and get experimenting. Just start at the minimums on Hodgdon's site assuming you have a modern 30-06.