I have a Bushmaster HBar 20" barrel w/ 1/9 rifling. I somehow gone my lines crossed and was trying to work up a load w/ heavy bullets (77gr MatchKing HPBT, mimicking the army's MK262 MOD 0 Designated Unit Marksman ammo), of course that just didn't give me the accuracy I was looking for. After more research, I then realized my oops on trying to use heavy bullets. So now on to trying to find somewhere to start. I understand that 1/9 twist is good for approx 52/53 - 69grs or so. I have some 69gr Sierra MatchKing HPBT's, product #1380 for 1/7-10 twist barrels, that I was thinking of trying. I understand that many AR-15 HBar Match shooters use Varget, BLC2 and or Vintavuori 135 or 140, but I don't have those powders on hand. I list below the powders I do have & the loadings in the manuals I have. Lyman 49th - 69gr HPBT IMR4320 - 23.9 - 26.5 IMR4064 - 22.9 - 25.5 Reloader15 - 23.9 - 26.5 W748 - 23.6 - 26.3 Hornady 8th - 68gr BTHP H322 - 21.6 - 23.0 W748 - 23.4 - 25.8 Can any of yall maybe give me some suggestions on where to start with the Sierra 69gr HPBT, or should I go to a different powder or a different bullet. Any help would be greatly appreciated. Thanks for reading & thanks for any help. Hope yall have a happy holiday.