I usually just pick a powder that is known to work well in any given cartridge i.e. IMR 4064 for the 36-06 & .308 H4350 for the .260 or 6.5 creed or Retumbo for a 7mm or 300 win mag. Once I have found a load that shoots half MOA or better I just stop. I won't mess with it again unless I run out of powder and can't find what I want but that rarely happens.