Have a AR-10 Armalite-22" bbl-SS Bull bbl config.-1:8" twist,according to Armalite bbl was hand lapped three times.I am starting to develope accuracy loads for rifle using 139-142 gr bullets.I have the following powders-4064,4350,4831,RL19,H-414 and N150. Can anyone suggest a powder that I may...