Before you take a drill to the gas port, consider this. Mine would not lock back on 7.62 Nato ammo when new. .308 ammo, no problem. Now that I have several hundred rounds downrange, it has no problems with 7.62 ammo.
Could your rifle just need breaking in? Oh, in all my AR's, I remove the bolt group prior to shooting and hose it off with CLP. Shake off the excess, reinstall and shoot!
chris