16" Gunner-profile .338 ARC barrel in 416R stainless with nitride, a 1:8 twist that matches the current SAAMI drawing, and 5/8x24 muzzle threads.

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Faxon Firearms Match Series AR-15 .338 ARC Threated AR Barrel, 16in, Gunner Profile, Pistol Length, 1-8 Twist, Black, 15B338A8P16NGQ-5R-NP3
The Faxon Gunner 16" barrel is chambered in .338 ARC with a maker-listed 1:8 twist, pistol-length gas system, and 5/8x24 muzzle threads. The current SAAMI drawing also lists an optional 1:8 right-hand twist, so this is the standards-based all-around barrel in the guide.
Faxon's product page offers its Type 2 .136 bolt as the matching option for this barrel. Use that bolt, verify headspace after assembly, and select the magazine specified for the upper and lower host.
The barrel uses 416R stainless steel, a QPQ nitride finish, 5R rifling, and Faxon's Gunner profile. A 16-inch barrel supports a conventional rifle configuration and matches the test-barrel length Hornady uses for its published factory-ammunition velocities. Any suppressor must have maker-approved .338-inch bore clearance and meet the model's barrel, mount, and firing-schedule limits.

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Add the Faxon Gunner 16" 1:8 338 ARC Barrel to your build and see how it enhances your platform.