I want to put together a dedicated 300 Blk upper for hunting purpose.  It will be used with supersonic ammo only loaded with 105-125gr bullets.  I know I want a 16" barrel or maybe 14 1/2" with pinned muzzle break.  The issue I have is the optimal twist rate for supersonic loads.  I think 1-7" is too tight and 1-10" maybe too slow so I was thinking 1-8" or 1-9" twist.  Am I on the right track here?  Any suggestions?