07-23-2020, 01:26 PM
Sounds like one of three things or a combination of the three.
1- Wall thickness between the two forward lugs on your lower. Measured a Colt lower, it measures .098.
2- The height of the front lug on your upper. My Colt upper is .477.
3- The hole location on the front upper receiver lug. Without a proper sized plug gauge or an optical comparator, I can't get an accurate measurement. You could measure the wall thickness from the hole edge to the front, rear and bottom of the lug and get a fair idea compared to a known good milspec upper for comparison.
I'd give Mega a call and ask what compatibility issues you might have with your particular upper before I sent anything back for replacement.
1- Wall thickness between the two forward lugs on your lower. Measured a Colt lower, it measures .098.
2- The height of the front lug on your upper. My Colt upper is .477.
3- The hole location on the front upper receiver lug. Without a proper sized plug gauge or an optical comparator, I can't get an accurate measurement. You could measure the wall thickness from the hole edge to the front, rear and bottom of the lug and get a fair idea compared to a known good milspec upper for comparison.
I'd give Mega a call and ask what compatibility issues you might have with your particular upper before I sent anything back for replacement.