Purchase this service along with required parts to ensure a complete and proper upper assembly-
Barrel nut torqued to spec with Aeroshell 64
Gas block journal dimpled for gas port alignment
Gas block torqued to spec with Loctite 242
Muzzle device timed & torqued to spec
Handguard aligned & torqued to spec (with Loctite 242 when applicable)
Coiled roll pins installed
Bolt carrier cleaned and lubed with UWRCG