I have shot US 869 in my .338 Lapua, both with 250 grain and 300 grain bullets. With a fresh barrel, I was 1 MOA or better at 100 yards. My 300 grain charge weight was 103.5 grains. If you're not grouping even 3" at 100 yards, and if you don't think you're burning out all the powder, then I'd...