Description
The 400 Legend has quickly become a favorite for hunters who want serious knockdown energy with manageable recoil, and Faxon built this barrel to make the most of it. The Gunner profile is the star here: it keeps the heavier Government contour back near the extension where stiffness matters, then tapers to a lighter Pencil profile forward of the gas block. That moves weight rearward toward the shooter, so the rifle points naturally and doesn't wear you out when you're still-hunting through timber or running a full day at the range.
What Makes the Gunner Profile Worth It
Balance is the whole point. A muzzle-heavy barrel feels sluggish when you need to swing on a moving buck or hold steady off-hand, and the Gunner contour fixes that without giving up the rigidity that keeps groups tight. Paired with a carbine-length gas system and a Big Bore barrel extension sized for large-diameter straight-wall cartridges, cycling stays smooth and consistent shot after shot.
Steel and Build on the Faxon 400 Legend Barrel
This one is machined from certified 4150 CMV Mil-Spec steel with a 1:16 twist that stabilizes the heavy 400 Legend projectiles nicely. The salt bath nitride finish treats the bore and exterior for corrosion and wear resistance, and the muzzle wears an 11-degree target crown for clean, consistent bullet release. Threads are 11/16×24, so you can run most .40-caliber muzzle devices and suppressors, and the gas block journal measures .875 inches.
Faxon Quality Control You Can Trust
Faxon makes these in-house in Cincinnati, Ohio, from raw steel to finished barrel. Every one is stress relieved, air-gauge tested, and headspace checked with PTG precision gauges before it ships. It drops into any standard AR-15 upper set up for 400 Legend, making it a straightforward heart for a hunting build or a straight-wall carbine you'll be proud of.
Key Specifications
- Manufacturer: Faxon Firearms
- Model: Duty Series Gunner
- Manufacturer Part Number: 15A4L16C16NGQ
- UPC: 816341028500
- Caliber: .400 Legend
- Barrel Length: 16"
- Profile: Gunner
- Material: 4150 CMV Mil-Spec Steel
- Finish: Salt Bath Nitride (inside and out)
- Twist Rate: 1:16
- Gas System: Carbine-Length
- Gas Block Diameter: .875"
- Muzzle Threads: 11/16×24
- Muzzle Crown: 11-Degree Target Crown
- Barrel Extension: Big Bore
- Platform: AR-15
What’s Included
- Faxon Duty Series Gunner 400 Legend 16" barrel
Frequently Asked Questions
What twist rate does this Faxon 400 Legend barrel have and why does it matter?
This barrel uses a 1:16 twist, which is what you want for stabilizing the heavier straight-wall projectiles the 400 Legend is loaded with. It keeps common hunting bullet weights spinning fast enough for consistent accuracy out to typical deer distances. That combination is a big part of why the cartridge shoots so predictably.
Will the Gunner 400 Legend barrel drop into a standard AR-15 upper?
Yes. It fits any standard AR-15 upper receiver configured for the .400 Legend cartridge. You will need a 400 Legend bolt and magazines to complete the build, since those are caliber-specific and not included with the barrel.
What muzzle devices and suppressors work with this barrel?
The muzzle is cut with 11/16×24 threads, which is the standard pattern for .40-caliber straight-wall builds. That makes it compatible with most .40-caliber muzzle brakes, flash hiders, and suppressors. Just make sure any device you pick is rated for the bore diameter and 400 Legend pressures.
Why choose the Gunner profile over a heavier Government contour?
The Gunner profile keeps the stiff Government contour near the chamber where it counts, then thins out to a Pencil profile up front to shed weight. The result is a rifle that balances back toward your body, so it feels lighter in hand and swings faster on target. You still get the rigidity for solid accuracy without the muzzle-heavy fatigue of a full heavy barrel.





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