What chamber dies your gun have? If it has the Wydle chamber it was designed to shoot the heavy pills. I had one 7.5:1 twist and it would not shoot 55gr less than 2 moa. I ended up shooting the barrel out trying. Then replaced it with a Shilen 1:9 and it does wonderful. Now if you have the std 5.56 or 223R the odds are good on it be able too. Personally I would shoot in the 69gr weight and be happy. The RMR 69gr HPBT I found out from Jake that these will expand, so I will be trying these out when I round out of the 65gr SGK.
