Barrel extension shim vs loctite

[DownSouth]

I had to order my upper from Midway so I did not have an opportunity to check the fit up prior to the purchase. In the future I will try buy local so I can check the fit up prior to buying it. At this point the shim I used has taken up the slack but it is still unclear if it will be better or worse than the Loctite. At least if I can easily remove the shim and replace it with Loctite if it doesn't work out. I am going to take it out next weekend and try it out and see what happens. I hope it is accurate and has no feeding or ejecting issues.