Diamondback has stripped uppers in stock at the moment. They also have complete uppers available.
https://diamondbackfirearms.com/shop/upper-308-stripped-upper-receiver-2-5/
Welcome to the forum. Stop by the introductions and let us know more about you.
As far as an x39 upper is concerned, it does not need, nor will it work on, a large frame AR lower.
Welcome to the forum.
Can you post some more details about the build and some pictures of the point of concern? That would help a bunch to get some suggestions.
It's great to hear of the success! Don't be a stranger just because you have a functioning rifle. This is a great hangout to shoot the sh!t and have some relaxing fun.
Welcome to the forum. I would have no different words of advice...lots of lube before and during shooting and shoot it before trying to change anything.
https://www.kcra.com/article/sacramento-mass-shooting/39618652#
@Robocop1051 any insight into this that is not being reported?
It is already being used to call for more gun laws. 😡