FAXON DUTY SERIES GUNNER PROFILE 11.5" CARBINE-LENGTH 5.56 NATO AR15 BARREL

Rifle Barrels › Duty Series › 5.56 NATO / .223 › 11.5″ Gunner, Carbine-Length  |  Works with: 5.56 BCG • .625″ gas block • carbine-length gas tube • 1/2x28 muzzle devices • 5.56 suppressors

Why an 11.5″ With Carbine Gas

Eleven and a half inches is the length the short 5.56 settled on: long enough to send 55 gr out at about 2,750 fps and keep it fragmenting past 100 yards, short enough to move through a doorway or clear a truck cab with a can on, and it is the length the carbine gas system was designed to run. A carbine port 7.66″ from the breech leaves four inches of barrel past it on an 11.5″, which is more dwell than a 10.5″ has and enough that the port can be reamed small, .068″ here, and still cycle a standard buffer with any factory ammunition. That is why nearly every issued 11.5″ is carbine gas: it works, with everything, without being tuned. Faxon builds this barrel for the shooter who wants that, a short gun that runs first time, every time, with the parts already in the box. It is also the right choice for a pistol or SBR that will mostly shoot unsuppressed.

Faxon makes two 11.5″ Gunners, and the difference is the gas system. The 11.5″ mid-length Gunner moves the port two inches out for a softer cycle and less gas at your face with a suppressor; it runs a .110″ port and is built to be tuned with an adjustable block, which is why suppressed-SBR shooters and the teams that build for work order it. This carbine-gas version is the one for everyone else: the same 4150 blank, the same Gunner profile, the same .625″ journal and 1/2x28 muzzle, with a gas system that needs nothing from you. The profile does the rest: a .980″ chamber journal and a Government taper from .674″ to .610″ behind the block keep the barrel stiff and give it the heat capacity to shoot strings without walking; a .750″ step, a .625″ journal, and a .500″ section ahead of it strip the weight a heavier profile carries at the muzzle for no return. At 1.14 lb it weighs what the mid-length does. If you want more dwell and a smaller port still, the 12.5″ mid-length Gunner is an inch longer; if you want the heaviest short barrel Faxon makes, the 10.5″ SOCOM is it.

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, and it adds virtually nothing to the surface: a few ten-thousandths of an inch, roughly a tenth the width of a human hair. 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 .2195″ 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 six grooves, right-hand, one turn in 8 inches, to a .2250″ 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 .625″ gas journal is turned to .6240–.6247″ and checked with a micrometer on every barrel, held within .005″ of the bore, the .500″ forward section is turned true to the same axis, and the 1/2x28 muzzle is threaded and crowned. Then the breech end: the Government taper, the .980″ chamber journal, and the extension thread.
5. Chamber The 5.56 NATO chamber is cut and checked with a headspace gauge; chamber surfaces are held to a 20 Ra finish.
6. MPI and nitride The machined barrel is 100% wet magnetic-particle inspected for surface and near-surface flaws, then salt-bath QPQ nitrided inside the bore and out, hardening the surface while adding virtually nothing to it.
7. Gas port, extension, pin After nitride, the .068″ gas port is drilled and reamed through the .625″ journal, the M4 extension is torqued to 150 ft-lb and pinned, and the barrel is headspaced with a 5.56 go/no-go gauge.
8. Mark The Faxon shield and order number are laser-engraved on the chamber journal and “5.56 NATO 1-8T” 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.

The carbine-gas 11.5″ is new for 2026 and has no reviews on FaxonFirearms.com yet; the mid-length 11.5″ Gunner it shares its blank and profile with is rated 5.0 across 19 reviews here, the 5.56 Gunner family averages 4.6 stars across 68 reviews at OpticsPlanet, and the Duty Series 5.56 line holds 4.7 across 25 at MidwayUSA.

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 11.5″ Gunner 5.56 FAQs

Is this a 5.56 NATO or .223 Remington chamber?

5.56 NATO, headspaced with a 5.56 go/no-go gauge after the extension is installed. A 5.56 chamber has the longer throat that lets it fire both 5.56 NATO and .223 Remington safely; the reverse is not true, so a .223-chambered barrel should not be fed 5.56.

Why carbine-length gas on an 11.5″ barrel, and what does it need to run?

Because carbine gas is the system the 11.5″ 5.56 was designed around, and on this length it needs nothing from you. The port sits 7.66″ from the breech with about four inches of barrel past it, which is enough dwell that Faxon can ream the port to .068″, a small port by SBR standards, and have the barrel cycle 5.56 NATO and full-power .223 on a standard carbine buffer and spring with no adjustable block and no tuning. That is the difference between this barrel and Faxon’s mid-length 11.5″: the mid-length moves the port two inches out for a softer, suppressor-friendly cycle and needs a .110″ port and an adjustable block to get there; this one keeps the port where every issued 11.5″ has it and runs out of the box. Add a can and an adjustable block will tame the extra gas, but it is not required to make the gun run. This barrel needs a carbine-length gas tube.

What is the Gunner profile?

Faxon’s hybrid contour: a full-diameter chamber journal and a Government taper behind the gas block where the steel does the most work, then a .750″ step, a .625″ gas journal, and a .500″ section toward the muzzle where mass adds weight without adding stiffness. At 11.5″ it weighs 1.14 lb, close to a Pencil in weight and closer to a Government profile in rigidity and heat capacity, and it takes the same .625″ low-profile block as every 5.56 Gunner. It is the profile Faxon is best known for.

What bullet weights does the 1:8 twist stabilize?

Everything from 55 gr FMJ through 69 and 77 gr match bullets. 1:8 is the most versatile twist for a general-purpose 5.56; 1:7 is only needed for the longest tracer and 80-plus grain projectiles, and 1:9 starts to run out of spin above 69 gr.

What gas block and gas tube does it take?

A .625″ gas block on the 1.9″ journal and a carbine-length gas tube. Faxon makes a .625″ adjustable and a .625″ fixed low-profile block, and a 304 stainless carbine-length gas tube. The gas port is reamed to .068″.

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 while adding virtually nothing to it: the surface grows by a few ten-thousandths of an inch, .0002–.0004″, roughly a tenth the width of a human hair or about the diameter of a single red blood cell. 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 M4 extension installed, torqued, pinned, and headspaced. Gas block, gas tube, and muzzle device are sold separately; the muzzle is threaded 1/2x28.

Will it work with a suppressor?

Yes. The 1/2x28 muzzle takes any 5.56 direct-thread can or mount, and carbine gas on an 11.5″ runs suppressed with more back pressure and gas at the charging handle than the mid-length version, which is the reason the mid-length exists. For a gun that runs suppressed most of the time, pair it with the Faxon .625″ adjustable gas block so you can bring the gas down.

Carbine gas or mid-length gas on an 11.5″?

Carbine gas, this barrel, if you want an 11.5″ that runs everything on a standard buffer with no tuning, will shoot mostly unsuppressed, or has to work as a duty gun with whatever ammunition it is handed. Mid-length gas, the 11.5″ mid-length Gunner, if the gun will live with a suppressor on it and you are willing to set it up with an adjustable block: the port two inches farther out gives a softer unlock and far less gas at your face, at the cost of margin. Same blank, same profile, same weight; the gas system is the whole difference.

Do I need an adjustable gas block?

Not to run it. The .068″ port and four inches of dwell are sized so the barrel cycles 5.56 NATO and .223 with a standard carbine buffer and spring, and a fixed block is the right part for an unsuppressed gun. If you add a suppressor, Faxon’s .625″ adjustable gas block lets you turn the gas back down for less recoil and less gas at the charging handle.

How fast does 5.56 leave an 11.5″ barrel?

Roughly 2,700 to 2,800 fps with 55 gr ammunition and 2,600 to 2,700 with 62 gr, depending on the load, or about 300 fps less than a 16″. The extra inch over a 10.5″ buys about 50 to 75 fps and, more usefully, another inch of dwell for the gas system. That keeps 55 and 62 gr loads above fragmentation velocity to about 100 yards and 77 gr open-tip loads working past 200, which is the range a 5.56 SBR is built for.

Can I put an 11.5″ barrel on my AR?

A barrel under 16″ makes the firearm either a pistol or a short-barreled rifle under federal law. Build it on a lower that has only ever been a pistol, or on a lower registered as an SBR with an approved Form 1 or Form 4, and check your state law before you buy. An 11.5″ cannot be pinned to 16″ with a normal muzzle device; that is what the 14.5″ is for. Faxon cannot advise on your specific configuration.

Is the gas journal dimpled for set screws?

No. The journal ships round so any .625″ 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.