I went to the range today to test fire my 10.5" Pistol build using this barrel and the bolt would not close on a live round using three different types of ammo (prvi partisan .223 62 grain brass, prvi partisan M193 brass and Federal XM193 brass). I also tried a known good bolt carrier group but had the same result. I didn't want to post this in here but my email that I sent using your contact info didn't go through.
All three times I had to separate the lower from the upper and pry the bolt carrier out of the chamber. In my opinion I believe the chamber to be out of spec. Any help would be appreciated.
Edit: By looking at the neck/shoulder of the brass case you can see that by the marks it makes on them it's not going in far enough, its just too tight.
https://www.rainierarms.com/?page=shop/detail&product_id=2909