Ready-to-install barrel. 1:12 twist. Muzzle threaded 5/8-24. .875″ gas block journal.
If you experience feeding problems with your completed upper, 99% of the time, the issue is due to the customer using a sub-standard bolt from an alternate manufacturer. The construction of the bolt, extractor, and ejector are all extremely important for proper feeding of the 375 SOCOM cartridge.