The AR-15 and 308 use the same magazine catch. Are you sure the mags are seating? Which CMMG lower and what mags are you using? How about some pictures of both sides of the receiver (focus on the mag catch parts) as well as a shot of the interior of the magwell.
After a bit of pondering I decided on an SI DEFENSE build. I would have like to try the Fail Zero stuff as well as the new bolt carrier group but it's too much for the budget on this weapon. I ordered a Generation II upper today and will order the lower next week after I complete a side job for cash :) Details to follow <thumbsup>
Hi Crackerbacks, FYI you wont get anywhere with that group buy at any of my sites. Sorry http://308ar.com/forum/index.php/topic,747.msg5136.html#msg5136