so i get my new kac ras for my 6721 it goes on no prob.  i am checking to see how solid it is and there is some play so i look over the upper and it is between the barrel and the upper! so if i can feel a definate change between the upper and barrel something is way wrong. i got out my varminter and there is zero play. so i took of the ras thinking it was the handguards alas it is the barrel and the upper. i only have 1k rounds thru it. so should i take her down and tighten barrel nut or ship her off to colt? no wonder my aimpont or irons would't repeat very well

well i said f it and took off the gas tube and grabbed the delta ring with my hand and spun it right off. THANKS COLT!! now i'll do it correctly. the way it should have been assembled in the first place.