Rebarreling an AR upper.

[LVLAaron]

For the same reasons as OP I bought a White Oak Precision Krieger barrel. WOP barrels use a barrel extension that is 1 thou oversized, so it's tight in the upper, which I believe to be essential for precision.

https://www.whiteoakarmament.com/white-oak-precision-service-rifle-barrels.html

Here's how it groups: https://imgur.com/a/0Rdd6nd