FAXON DUTY SERIES GUNNER PROFILE 16" MID-LENGTH .308 WIN AR10 BARREL

Rifle Barrels › Duty Series › .308 Win › 16″ Gunner, Mid-Length  |  Works with: .308-family BCG • .750″ gas block • mid-length gas tube • 5/8x24 muzzle devices • .30 cal suppressors

Why a 16″ Mid-Length .308 Gunner

Sixteen inches is the length that makes a .308 an AR-10 carbine: legal with no paperwork, short enough to move through a doorway or a truck cab, and still fast enough to send a 168 gr match bullet out at about 2,550 fps and a 150 gr hunting bullet at 2,650. The catch has always been the gas system. Most 16″ .308 barrels use carbine-length gas, which taps a big cartridge early and hard and produces the slam, the torn brass, and the muzzle climb AR-10s are known for. Mid-length gas moves the port out to about 9.8″ from the breech, where pressure is lower and there are six inches of barrel past it, and the difference is the whole character of the rifle: a longer, softer push on the carrier, brass that comes out intact, a sight picture that stays put, and a suppressor that goes on without a fight.

The Gunner profile, which Faxon called the Big Gunner on AR-10 barrels until it simplified its naming in 2026, is how the carbine loses the weight. A 1.200″ extension shoulder, a .750″ body behind the gas block, and a .875″ step at the block keep the barrel stiff and give it heat capacity where a .30-caliber bore needs it; a .750″ gas journal and a .600″ section ahead of it strip the mass that a straight heavy profile carries at the muzzle for no return. At 1.91 lb it weighs about what a heavy-profile 16″ 5.56 barrel does, so a .308 built on it balances like a carbine, and owners report it outshooting the factory barrels it replaced with half-MOA to 1.2 MOA groups with match ammunition. If the rifle will shoot far more than it will move, the 18″ rifle-gas Gunner adds 75 fps and the softest gas system there is; the 16″ Pencil is the same length lighter still; and the 13.9″ Gunner makes a 16″ rifle with a pinned device.

What “Duty Series” Means

Duty Series is Faxon’s 4150 CMV line: the M4/M16 barrel alloy, salt-bath QPQ nitrided inside and out. 4150 carries about 0.50% carbon plus vanadium, which gives it more strength and wear resistance at temperature than 4140, and nitride adds a hard, corrosion-resistant surface to the bore and exterior without plating anything, so the rifled dimensions Faxon air-gauges before treatment are the dimensions you get. It is the right combination for a barrel that will be shot hard, carried in the weather, and cleaned when there is time. Faxon’s stainless Match Series is the option when you want the precision-barrel formula; the Duty Series is the one to reach for when the rifle has a job.

What’s in the Box

How It’s Made

Every Duty Series barrel is made start to finish in Faxon’s Greater Cincinnati plant, on Faxon’s machines, to Faxon’s prints. This is the routing for this barrel.

1. Drill and pull-ream 4150 CMV bar is gun-drilled, then pull-reamed from the chamber end to a .3015″ bore held to ±.001″, with a 32 Ra maximum finish checked on a profilometer and a borescope pass for reamer marks.
2. Button rifle A carbide button is pulled through from the chamber end to form four grooves, right-hand, one turn in 10 inches, to a .3095″ groove diameter. Bore and groove are air-gauged.
3. Stress relieve and qualify The rifled blank is stress relieved before it becomes a finished barrel, then the OD is qualified true to the bore so every later cut references the same axis.
4. Turn the Gunner profile Muzzle end first: the .750″ gas journal is turned to .7490–.7497″ and checked with a micrometer on every barrel, held within .005″ of the bore, the forward section is turned from .600″ to .575″ true to the same axis, and the 5/8x24 muzzle is threaded and crowned. Then the breech end: the .750″ body, the .875″ step, the 1.200″ extension shoulder, and the 1-16 extension thread.
5. Chamber The .308 Win chamber is cut and checked with a headspace gauge; chamber surfaces are held to a 20 Ra finish.
6. Extension, gas port, pin The DPMS-pattern .308 extension is torqued to 150 ft-lb, the .081″ gas port is drilled and reamed through the .750″ journal, the extension is pinned, and the barrel is headspaced with a .308 go/no-go gauge.
7. Nitride and mark Salt-bath QPQ nitride inside and out, then the Faxon shield and order number are laser-engraved on the chamber journal and “.308 WIN 1-10T” ahead of the gas block.

What Reviewers and Owners Say

Voted Favorite Aftermarket Barrel by Shooting Sports Retailer every year since 2022 — the Gold Award, the top honor in the category. Faxon also took the Tactical Retailer Gold Award in the same category in 2025. Here is what independent testers and buyers have said about Faxon barrels and this one.

5.0 stars across 4 reviews on FaxonFirearms.com. Elsewhere: Faxon’s .308 Gunner barrels average 4 stars across 13 reviews at OpticsPlanet, and this 16″ has owner reviews at Primary Arms.

Build It Out: Faxon Parts That Fit This Barrel

Everything below is made or specified to the same prints this barrel is, so the gas system, extension, and muzzle line up the first time. Pick one from each row and the upper is done.

Duty Series 16″ Gunner .308 FAQs

Is this a .308 Winchester or 7.62x51 NATO chamber?

.308 Winchester, headspaced with a .308 go/no-go gauge after the extension is installed. 7.62x51 NATO is loaded to lower pressure than commercial .308 and runs fine in it; it runs surplus M80 fine, though one owner notes his barrel groups match ammunition far better than M80, which is true of most .308s. Headspace is set at the factory with a go/no-go gauge after the extension is installed.

Why mid-length gas on a 16″ .308?

Because carbine-length gas is why most 16″ AR-10s are unpleasant. A .308 pushes twice the gas of a 5.56 at the port, and a carbine port on a 16″ .308 taps it early and hard: a violent cycle, battered brass, and a rifle that does not want to stay on target. Mid-length puts the port about 9.8″ from the breech with six inches of barrel past it, where pressure is lower and the carrier gets a longer, gentler push, so the bolt unlocks later, brass comes out intact, and the recoil impulse spreads out. It is the system that makes a 16″ .308 shoot like a rifle instead of a shotgun, and it is the friendlier one for a suppressor. Faxon reams the port to .081″ and owners run it with a standard AR-10 carbine buffer, suppressed and not. This barrel needs a mid-length gas tube; on a DPMS-pattern upper the standard mid-length tube reaches the port.

What is the Gunner profile on an AR-10, and what happened to “Big Gunner”?

Same barrel, simpler name: Faxon dropped the “Big” in 2026 so its AR-15 and AR-10 Gunner barrels share one profile name. On an AR-10 it means a .750″ body behind the gas block, a .875″ step and a .750″ gas journal at the block, then a .600″ section tapering to .575″ toward the muzzle where mass adds weight without adding stiffness. On a 16″ .308 it weighs 1.91 lb, against roughly three pounds for the heavy-profile barrels most AR-10s are built with, and it takes the most common AR gas block.

What bullet weights does the 1:10 twist stabilize?

The whole .308 range: 147 and 150 gr ball and hunting loads, 168 and 175 gr match bullets, and 180 gr hunting bullets. 1:10 is the .308 standard for a reason; 1:12 runs out of spin at the heavy end and 1:8 gains nothing with anything a gas gun feeds. From a 16″ barrel a 168 gr match bullet leaves at about 2,550 fps, which keeps it supersonic to about 1,000 yards.

What gas block and gas tube does it take?

A .750″ gas block on the 1.9″ journal and a mid-length gas tube. Faxon makes a .750″ adjustable and a .750″ fixed low-profile block, and a 304 stainless mid-length gas tube. The gas port is reamed to .081″.

What does 4150 CMV mean?

Chrome-moly-vanadium steel with about 0.50% carbon, the alloy the M4 and M16 barrel specification calls for. The higher carbon and the vanadium give it more strength and wear resistance at temperature than 4140, which matters most on a barrel that will see fast strings and sustained fire.

Is the nitride inside the bore?

Yes. Salt-bath QPQ nitride is a diffusion treatment, not a plating, so it hardens the surface of the bore and the exterior without adding thickness or changing the rifled dimensions that were air-gauged before treatment. It also gives the barrel its corrosion resistance and matte black finish.

Does it come with a gas block, gas tube, or muzzle device?

No. It ships with the black-oxide DPMS-pattern .308 extension installed, torqued, pinned, and headspaced. Gas block, gas tube, and muzzle device are sold separately; the muzzle is threaded 5/8x24.

Will it work with a suppressor?

Yes. The 5/8x24 muzzle takes any .30-cal direct-thread can or 5/8x24 mount rated for .308, and mid-length gas is the friendlier system for a suppressed 16″ .308, with less back pressure and less gas at the charging handle than carbine gas. For a rifle that runs suppressed most of the time, pair it with the Faxon .750″ adjustable gas block so you can bring the gas down.

How fast does .308 leave a 16″ barrel, and what does it give up?

Roughly 2,600 to 2,700 fps with 147 and 150 gr, 2,500 to 2,600 with 168 gr, and 2,450 to 2,500 with 175 gr, depending on the load, or 50 to 75 fps less than an 18″ and about 125 less than a 20″. That is still enough to keep a 175 gr match bullet supersonic to about 1,000 yards and a 150 gr hunting bullet expanding past 400, in a rifle that is two inches handier than an 18″ and four handier than a 20″. The 16″ gives up little the cartridge needs and gains the handling the AR-10 has always lacked.

Is the gas journal dimpled for set screws?

No. The journal ships round so any .750″ low-profile, clamp-on, or pinned gas block fits the 1.9″ journal. A set-screw block holds on the nitrided journal when its screws are torqued with thread locker; if you want dimples, mark them through the block’s screw holes and drill.

Where is it made, and what is the warranty?

Made in Greater Cincinnati, Ohio, from bar stock to finished barrel, and covered by the Faxon Lifetime Guarantee.

Dimensions are from the Faxon engineering print and inspection sheets for this SKU; weight is nominal. Gas block, gas tube, and muzzle device sold separately. Owner reviews are quoted as written from FaxonFirearms.com product reviews; press quotes link to their sources. Award: Shooting Sports Retailer Choice Awards, Favorite Aftermarket Barrel, Gold. Covered by the Faxon Lifetime Guarantee.