Recently upgraded to the Magpul MOE comm spec stock and noticed an unusual amount of play whether it’s collapsed down or extended out over the receiver extension tube. The OEM stock fit snug and had zero play.
The lower is an EA w/ a standard receiver extension assembly.
What is a standard receiver extension? There are two types- military and commercial. It is quite possible that you had a milspec one on the lower which is 1.14 in. Commercial tubes are 1.17. My guess is that is the issue.