Alright dudes, update here. After more messing around with it this morning I found the issue. In the first photo you’ll see some marks near the crown. There’s an index point inside the can, looks like a gear wheel, which the muzzle slides through. I noticed it was binding up at this point. Using several high grit sandpapers and some patience I made passes around the muzzle until the can fit snug. Perfect fit now, no issues with it going on or off. Not sure if this is an actual issue on the builders end or GA, or if this is a common occurrence with even the original MK11 cans requiring a little more attention to fitting at times. Could be why builders occasionally want you to supply a MK11 when having the barrel done.
*Don’t do this if you don’t feel comfortable with it*
