FAXON DUTY SERIES LIGHT TAPERED 10.5" 9MM BLOWBACK AR15 BARREL

Rifle Barrels › Duty Series › 9mm › 10.5″ Light Taper, Blowback  |  Works with: 9mm BCG • 1/2x28 9mm muzzle devices • HUB adapter • 7″ handguard

Why a 10.5″ 9mm, and What Makes a PCC Barrel Different

A 9mm AR is a different machine from a 5.56 AR, and the barrel shows it. There is no gas system: the bolt is held closed by its own mass and a heavy buffer, and pushed open by the case, so the barrel has no port, no journal, and no gas block, only a taper from the receiver to the muzzle. There is no separate barrel extension either. Faxon turns the shank that fits the upper receiver directly into the barrel, presses a .125″ index pin into it so the barrel cannot rotate under the barrel nut, and cuts the chamber with a radiused, chamfered mouth that feeds from Glock- and Colt-pattern magazines without a ramp. Because the chamber is part of the barrel, 10.5″ is measured from the breech face to the muzzle, and about 1.1″ of it is chamber.

10.5″ is the 9mm length for a pistol or SBR that gets a full-length handguard. It buys about 50 fps over an 8.5″, a longer sight radius for irons or a dot-and-magnifier, and nine inches of barrel ahead of the receiver for a 7″ or 9″ rail, a hand stop, and a light, in a gun that is still short enough to shoulder in a hallway. Most 147 gr loads stay subsonic for a can. The Light Taper profile keeps the weight off the muzzle for the same reason a Gunner does on a rifle: a 9mm AR does not need heat capacity, it needs to swing fast and stay balanced with a heavy buffer and bolt in the back. If the gun lives in a bag, the 8.5″ 9mm is the same barrel two inches shorter; the 16″ makes a carbine that needs no paperwork.

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 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. On a 9mm barrel, where the enemy is lead and copper fouling rather than heat, the hard, slick nitrided bore is the feature you notice: it shoots clean and cleans with a patch.

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 .348″ 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 10 inches, to a .355″ 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 receiver shank The breech end is turned to the .999″ shank that fits the upper receiver, held to within .0008″, with the 1.170″ barrel-nut shoulder behind it. This is the feature a 5.56 barrel gets from a separate extension; here it is part of the barrel.
5. Turn the taper and muzzle The body is turned from .675″ at the shoulder to .625″ at the muzzle, true to the bore, the .720″ muzzle shoulder is formed, and the 1/2x28 muzzle is threaded and crowned.
6. Chamber The 9mm chamber is cut and checked with a headspace gauge, the chamber mouth is radiused and chamfered for magazine feeding, and chamber surfaces are held to a 20 Ra finish.
7. Pin, nitride, and mark The .125″ index pin is pressed into the shank, then the barrel is salt-bath QPQ nitrided inside and out and the Faxon shield, order number, and “9 x 19 1-10T” are laser-engraved.

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 buyers have said about Faxon 9mm barrels and this one.

4.0 stars across 4 reviews on FaxonFirearms.com. Elsewhere: Faxon’s 9mm barrels average 4.7 stars across 33 reviews at OpticsPlanet and 5.0 across 11 at MidwayUSA.

Build It Out: Faxon Parts That Fit This Barrel

A 9mm AR needs fewer parts than a 5.56, and the ones it needs matter more. Everything below is made or specified to the same prints this barrel is.

Duty Series 10.5″ 9mm Blowback FAQs

Is this a 9mm Luger / 9x19 chamber? What about +P?

Yes: a SAAMI 9mm Luger (9x19) chamber, cut with a 9mm headspace gauge and marked 9 x 19 1-10T on the barrel. Standard and +P ammunition are fine; +P+ and 9mm Major are not SAAMI loads and are not recommended in a blowback gun.

Why is there no gas port?

Because a 9mm AR is a blowback gun. The bolt is not locked; it is held closed by the weight of the bolt carrier and buffer, and the case pushes it open after the bullet leaves. That is why the barrel has no port, journal, or gas block, and why the buffer and bolt weight matter so much in a 9mm build (see below).

Will it feed from Glock magazines? Colt magazines?

Both. The chamber mouth is cut with a radius and a wide chamfer instead of the M4-style feed ramps a 5.56 barrel gets from its extension, so rounds coming in from a Glock-pattern lower or a Colt-pattern lower both find the chamber. Faxon’s 9mm BCG is likewise cut for both patterns. The lower’s magazine well and feed geometry still matter; if a build nosedives rounds, look at the lower’s ramp before the barrel.

Does it use a standard AR barrel extension?

No. The extension is part of the barrel: the .999″ shank that fits the upper receiver, the barrel-nut shoulder, and the index pin are all machined into the same piece of 4150 CMV, and the pin is pressed in at Faxon. It drops into any mil-spec AR-15 upper with a standard barrel nut and any 9mm handguard, and it is not removable. The Faxon 9mm BCG is the matching bolt.

What bullet weights does the 1:10 twist stabilize?

All of them. 1:10 is the standard 9mm twist and handles 115, 124, and 147 gr, jacketed or coated, supersonic or subsonic. 147 gr stays subsonic from a 10.5″ and is the load for a suppressed 9mm pistol.

What buffer and spring does a 9mm blowback need?

A heavy one. With no gas system, the buffer and bolt mass are what keep the breech closed long enough for pressure to drop. Most 9mm builds run a 5.5 to 8 oz 9mm buffer with a standard carbine spring; a dedicated 9mm lower may use its own. Faxon’s full-mass 9mm BCG has a removable carrier weight so you can tune reciprocating mass to the buffer you run. Start heavy; a light buffer in a blowback gun is hard on the bolt, the lower, and the shooter.

Is 10.5″ the overall length?

Yes, breech face to muzzle, which is how barrel length is measured. On a 9mm AR the chamber is part of the barrel rather than the extension, so about 1.1″ of the 10.5″ is chamber, and about 9.3″ is exposed ahead of the receiver face. Muzzle threads take the last .62″.

What muzzle devices fit? Can I use a 5.56 device?

Any 1/2x28 device with a 9mm bore: Faxon’s MuzzLok 9mm flash hider, 9mm A2, or Plan B 9mm devices. Do not use a 5.56 device even though the threads match: a .223 bore will not pass a 9mm bullet. The threads are .62″ long, the AR standard, so rifle-pattern devices seat on the shoulder; devices made for .5″ pistol threads may bottom out and need a thread spacer.

Will it work with a suppressor?

Yes, with two notes. Use a fixed-barrel spacer or a direct-thread or fixed mount, not a recoil booster (Nielsen device), because the barrel does not move; and check the mount’s thread depth against the .62″ AR-length threads. Faxon’s 1/2x28 HUB adapter fits any HUB-pattern can. With 147 gr subsonics, a 10.5″ 9mm is one of the quietest things you can suppress.

How fast does 9mm leave a 10.5″ barrel?

About 1,300 to 1,350 fps with 124 gr, 1,350 to 1,400 with 115 gr, and 1,020 to 1,070 with 147 gr, depending on the load, or roughly 50 fps more than an 8.5″ and 50 fps less than a 16″ carbine. 9mm gains most of what a longer barrel can give it in the first eight inches, so the 10.5″ is less about velocity than about sight radius and rail length. Most 147 gr loads stay subsonic; if a can is the plan, pick a 147 gr load rated under 1,050 fps.

Can I put a 10.5″ 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. Faxon cannot advise on your specific configuration.

My build runs ball ammo but not hollow points or aluminum cases. Is it the barrel?

Almost never. A blowback 9mm feeds from the magazine lips, over the lower’s ramp, and into a chamber mouth that on this barrel is radiused and chamfered to accept both Glock- and Colt-pattern presentation; the chamber itself is a SAAMI 9mm cut to a gauge. When brass FMJ runs and blunt hollow points or aluminum-cased ammunition do not, the round is stalling before it reaches the chamber: a magazine with worn or out-of-spec lips, a lower whose ramp sits too low or too far back for the bullet profile, or a bolt that is arriving too early or too late because the buffer weight is off for the load. Start with factory magazines, a 5.5 to 8 oz buffer, and the Faxon 9mm BCG with its weight installed, then try a different hollow point profile. If it still will not feed, call Faxon customer service with the lower, magazine, and ammunition you are running; they have seen most combinations.

What does 4150 CMV mean, and is the nitride inside the bore?

Chrome-moly-vanadium steel with about 0.50% carbon, the M4/M16 barrel alloy, which gives it more strength and wear resistance than 4140. Salt-bath QPQ nitride is a diffusion treatment, not a plating, so it hardens the bore and the exterior without changing the rifled dimensions Faxon air-gauges before treatment, and it gives the barrel its corrosion resistance and matte black finish. On a 9mm, where lead and copper fouling are the enemy, a hard, slick nitrided bore cleans with a patch.

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. BCG, buffer, and muzzle device sold separately. Owner reviews are quoted as written from FaxonFirearms.com and dealer product reviews; press quotes link to their sources. Award: Shooting Sports Retailer Choice Awards, Favorite Aftermarket Barrel, Gold. Covered by the Faxon Lifetime Guarantee.