I just got my stag model 5 (6.8 spc) and on the 7th round I had a double feed with the c products mag. that came with the rifle. The empty case was not extracted and the new round was jammed in with it. Is this a mag problem or a rifle problem. I was sighting in an eotech sight from the sitting position and had the rifle supported with weight on the magazine. Could that have caused the problem?? (I shoot my 5.56 this way and have never had a problem). I called stag and they said they would fix any problems if I it continues to happen. but I don't have enough ammo to really test it (have a shippment of ammo on the way). Any thoughts would be welcome.
I would agree the double feed is not a lube issue. It is more a mag or extractor issue like you stated. At least with when it happened to me this seemed the root cause.
I will say though get ready to hand cycle the 6.8. It is finicky at first but gets under way when done. Maybe you can use the lube and report back. I have never heard of it before. I am a EWL and tw25 guy right now when they all run out (if ever) then I am giving the home brew Mobil one,Lucas,stp mix a shot.