FAXON DUTY SERIES GUNNER PROFILE 16" CARBINE-LENGTH .458 SOCOM AR15 BARREL

Rifle Barrels › Duty Series › .458 SOCOM / .450 Bushmaster › 16″ Gunner, Carbine-Length  |  Works with: .458/.450 BCG • .875″ gas block • carbine-length gas tube • 11/16x24 muzzle devices

Why a 16″ .458 SOCOM, and Why the Gunner Profile

.458 SOCOM was designed after Mogadishu to put a big-bore round in a standard M4: a .458″ bullet from a rebated-rim case that fits a 5.56 magazine, runs on a standard upper and lower, and needs only a bolt with a .308-size face. It is the cartridge for a hunter who wants .45-70 energy in an AR where straight-wall rules do not apply, for a hog rifle that stops what it hits, and above all for a suppressed big bore: 500 to 600 gr subsonics at 1,000 fps through a .458-rated can are as quiet as a .300 Blackout and hit like a slow .45-70. From a 16″ barrel a 250 gr load leaves at about 2,100 fps and a 300 gr at about 1,900, with enough left to kill deer, hogs, and bear cleanly to 200 yards, which is where Faxon and the ammunition makers draw the line. Sixteen inches is the length Faxon recommends for the cartridge: the powder is burned early, so a longer barrel adds almost nothing, and a 16″ carries through the woods. The 10.5″ .458 SOCOM is the pistol or SBR that gives up little with subsonics.

A .458 bore takes most of the steel out of a 1″ blank, so this Gunner is built heavier than the 350 Legend and 300 Blackout versions: a .980″ chamber journal, a straight .875″ body behind the gas block instead of a Government taper, an .875″ gas journal, and a taper from .750″ to .725″ ahead of it. The body is where the barrel gets its stiffness and where the wall around the chamber and port has to be; the taper is where a barrel gets heavy without getting stiffer. At 16″ the result is 1.72 lb, about six ounces over the 350 Legend Gunner and still lighter than most heavy-profile 5.56 barrels, in a rifle that recoils like a 20-gauge with supers and like a 5.56 with subs. A carbine-length gas system with a .109″ port runs the low-pressure cartridge with a standard buffer, and the 11/16x24 muzzle takes Faxon’s MuzzLok .450/.458 brake or a .458-rated can. If you hunt in a straight-wall state, the 16″ .450 Bushmaster Gunner is the same barrel with a straight case that the game laws allow; the 16″ 350 Legend Gunner is six ounces lighter and runs a 5.56 bolt.

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 .451″ 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 14 inches, to a .458″ 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 .875″ gas journal is turned to .8740–.8750″ and checked with a micrometer on every barrel, held within .005″ of the bore, the Gunner taper ahead of it is turned true to the same axis, and the 11/16x24 muzzle is threaded and crowned. Then the breech end: the .875″ body, the .980″ chamber journal, and the extension thread.
5. Chamber The .458 SOCOM 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 .109″ gas port is drilled and reamed through the .875″ journal, the Big Bore M4 extension is torqued to 150 ft-lb and pinned, and the barrel is headspaced with a .458 SOCOM go/no-go gauge.
8. Mark The Faxon shield and order number are laser-engraved on the chamber journal and “.458 SOCOM 1-14T” 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 2 reviews on FaxonFirearms.com and 5.0 across 3 at OpticsPlanet; the .458 SOCOM Gunner line is also reviewed at Brownells.

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 .458 SOCOM FAQs

What bolt, upper, and magazines does a .458 SOCOM barrel need?

The chamber is cut to the .458 SOCOM specification and headspaced with a .458 SOCOM go/no-go gauge after the extension is installed. The cartridge was designed around the AR-15 with a rebated .473″ rim, so it fits a standard lower and uses a bolt with a .308-size face: Faxon’s .458 SOCOM / .450 Bushmaster bolt and bolt carrier group have the .125″ bolt-face depth the cartridge calls for, and a 5.56 bolt will not work. The upper receiver has to match it: Faxon requires its Enhanced Forged Big Bore upper for every .458 SOCOM and .450 Bushmaster barrel, because its feed ramps and ejection port are opened up for the .541″ case and a standard 5.56 upper will not feed and eject it reliably. Magazines are the easy part: .458 SOCOM was designed to single-stack in an unmodified 5.56 magazine, so a 30-round 5.56 magazine holds about ten rounds; anti-tilt followers and magazines built for the cartridge feed most reliably. This barrel’s Big Bore extension has its feed ramps opened up for the case and ships headspaced. So the build is barrel, Big Bore upper, bolt, and magazines.

Why carbine-length gas on a 16″ .458 SOCOM, and what does it need to run?

Because .458 SOCOM is a low-pressure, fast-burning cartridge that needs its port early to catch enough gas: carbine-length puts it about 7.7″ from the breech with eight and a half inches of barrel past it, and Faxon reams it to .109″, a third larger than a 5.56 port, to make up for the lower pressure there. With factory 250 to 300 gr supersonic ammunition it cycles with a standard carbine buffer and spring and a .458 SOCOM bolt carrier group. Heavy subsonics (500 to 600 gr) make far less gas, so a gun that runs them, especially suppressed, wants an adjustable block and often a lighter buffer to cycle both. This barrel needs a carbine-length gas tube.

What is the Gunner profile, and why is the .458 SOCOM version built with a straight body?

Faxon’s hybrid contour: full diameter where the barrel gets its stiffness (the chamber journal and the body behind the gas block) and tapered ahead of the block where mass only adds weight. Because a .458″ bore leaves very little wall in a 1″ blank, the .458 SOCOM Gunner runs a straight .875″ body and an .875″ gas journal where the 5.56 Gunner runs a Government taper and a .625″ journal, and it tapers to .725″ ahead of the block instead of .500″. That is why it weighs 1.72 lb at 16″, and why it takes the .875″ low-profile block instead of the .750″.

Why 1:14 twist, and what bullets does it stabilize?

Because .458 SOCOM runs everything from 250 gr supersonics to 600 gr subsonics, and the long, heavy subsonic bullets need more spin than the 1:16 or 1:18 a .45-caliber hunting load would. Faxon rifles it 1:14 so the same barrel stabilizes 250 to 300 gr hunting loads at 1,900 to 2,100 fps and 500 to 600 gr subsonics at 1,000, which is the whole point of the cartridge: a rifle that hunts with supers and shoots quiet with a can. From a 16″ barrel a 300 gr load leaves at about 1,900 fps with roughly 2,400 ft-lb, which is .45-70 territory.

What gas block and gas tube does it take?

A .875″ gas block on the 1.9″ journal and a carbine-length gas tube. Faxon makes a .875″ adjustable and a .875″ fixed low-profile block, and a 304 stainless carbine-length gas tube. The gas port is reamed to .109″.

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 Big Bore M4 extension installed, torqued, pinned, and headspaced. Gas block, gas tube, and muzzle device are sold separately; the muzzle is threaded 11/16x24.

Will it work with a suppressor?

Yes. The 11/16x24 muzzle takes a .458-rated (.45-70 or .458 SOCOM rated) can on an 11/16x24 mount, never a .30-cal, .36-cal, or pistol-only .45 can, and a .458 SOCOM that switches between supers and heavy subsonics, especially with a can, needs an adjustable block to run both, and the can has to be rated for the cartridge. For a rifle that runs suppressed most of the time, pair it with the Faxon .875″ adjustable gas block so you can bring the gas down.

Is .458 SOCOM legal in straight-wall states, and how far will it hunt?

Usually not, and that is the one thing to know before choosing it over .450 Bushmaster. The .458 SOCOM case has a slight shoulder, so most states with straight-wall rules (Ohio, Michigan’s southern zone, Iowa, Indiana) do not allow it for deer; check your regulations, and if you hunt in one of those states, build the .450 Bushmaster instead. Everywhere a bottleneck rifle cartridge is legal, the .458 is a 200-yard deer, hog, and black bear round: a 300 gr bullet leaves a 16″ barrel at about 1,900 fps with roughly 2,400 ft-lb and carries enough velocity to expand to about 200 yards, which is where Faxon and the ammunition makers put the practical limit.

How fast does .458 SOCOM leave a 16″ barrel, and what about subsonics?

About 2,100 fps with 250 gr loads and 1,900 with 300 gr, depending on the load, or roughly 2,400 ft-lb at the muzzle. Subsonic loads with 500 to 600 gr bullets leave at about 1,000 fps and 1,100 to 1,300 ft-lb, which is more energy than a .45 ACP delivers at the muzzle, delivered quietly through a .458-rated suppressor. The cartridge burns its powder early, so a longer barrel adds very little; 16″ is the length Faxon recommends for a rifle, and the 10.5″ gives up little with subsonics.

.458 SOCOM or .450 Bushmaster?

.450 Bushmaster if you hunt in a straight-wall state: its case has no shoulder and it is legal where the .458 is not, and it hits about as hard with 250 gr supers. .458 SOCOM if straight-wall rules do not apply and you want the more versatile cartridge: a .458″ bullet with a huge range of factory and component bullets, from 250 gr supers to 600 gr subsonics, in a case that single-stacks in an unmodified 5.56 magazine, with a 1:14 twist that stabilizes all of it. The two share a bolt, an upper, a gas block, and a muzzle thread, so the rest of the build is the same.

Is the gas journal dimpled for set screws?

No. The journal ships round so any .875″ 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.