I think any rack grade barrel is luck of the draw. I consider the Brownells Satern/Liberty barrels has rack grade. I have three Friends who have bought the Brownells 18 6.5 Grendel barrels. Two Brownells barrels were out of the first batch with SAAMI chamber. Both barrels are pretty accurate but both were machined with short chambers. Both Friends reload so they decided to keep their barrels.
These Brownells were in the same production batch as those received by Midway (AR Stoner) where they also received many short chambered barrels. Satern/Liberty blamed everybody else for the problem then released the Grendel II chambered barrels. My third Friend bought a Brownells barrel last year and he is satisfied with his 18 Brownells. At least with Brownells warranty you should be able to resolve any issue should you encounter a problem.
These Brownells were in the same production batch as those received by Midway (AR Stoner) where they also received many short chambered barrels. Satern/Liberty blamed everybody else for the problem then released the Grendel II chambered barrels. My third Friend bought a Brownells barrel last year and he is satisfied with his 18 Brownells. At least with Brownells warranty you should be able to resolve any issue should you encounter a problem.