Product Overview
Faxon Duty Series 11.5″ Gunner 5.56 NATO AR-15 Barrel 4150 CMV | QPQ Nitride | 1:8 Twist | 1.14 lb | SKU: 15A58M11NGQ This is the Faxon barrel that suppressed-SBR builders, and the law enforcement teams who build them for work, order more than any other.
Mid-length gas on an 11.5″ is unusual: the port sits two inches farther from the chamber than a carbine system, so the bolt unlocks later and softer, and with a suppressor on there is far less back pressure and gas at your face.
Faxon opens the port to .110″ to make the short dwell work, and pairs it with a Gunner profile that keeps a Government taper behind the block and a straight .625″ section ahead of it, for 1.14 lb.
GUNNER PROFILE Government taper behind the block, straight .625″ ahead of it.
1.14 lb, with the mass where an SBR needs it.
4150 CMV, NITRIDED The M4/M16 barrel alloy, QPQ nitrided inside and out for hardness and corrosion resistance with no plating in the bore.
MID-LENGTH GAS Rare on an 11.5″, and the reason to buy this one: lower port pressure, a softer unlock, and far less gas in your face suppressed.
.110″ port, .625″ journal.
HEADSPACED & READY M4-ramp extension torqued to 150 ft-lb, pinned, and checked with a 5.56 go/no-go gauge.
1/2x28 muzzle.
Where the port sits decides how much pressure reaches the carrier and for how long, and that decides how hard the bolt unlocks, how fast the carrier moves, and how much gas comes back through the receiver.
A carbine-length port on an 11.5″ barrel opens about 7.7″ from the breech with four inches of barrel past it, so it sees high pressure for a long time; that is why a carbine-gas SBR runs anything you feed it and why it is harsh, especially suppressed.
This barrel moves the port to 9.66″.
Pressure there is lower and the bullet exits sooner after the port opens, so the carrier gets a gentler, shorter push.
The bolt unlocks later, when chamber pressure has fallen further, extraction is easier on the brass, the reciprocating mass moves slower, and with a suppressor on there is noticeably less gas venting at the charging handle and ejection port.
Faxon reams the port to .110″, larger than the .081″ on a 16″ mid-length, so that roughly two inches of dwell still deliver enough gas to run the gun.
The trade is margin.
A carbine-gas 11.5″ is overgassed on purpose; this one is built to be tuned, and it rewards it.
Around the shop it has a nickname, the gamer barrel, because the shooters who set it up with an adjustable gas block, pick a buffer, and dial it to their ammunition and their can end up with one of the softest 5.56 SBRs there is.
That is exactly the gun a SWAT team wants: an 11.5″ that runs suppressed all day without beating up the shooter or the bolt.
If you would rather have the margin than the tuning, the same profile is available with carbine-length gas, and the 10.5″ SOCOM is the heavier-contour option for a carbine-gas SBR.
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 INCLUDED 11.5″ Gunner barrel, 4150 CMV, QPQ nitride, 1:8 twist, laser-marked 5.56 NATO 1-8T INCLUDED M4 feed-ramp barrel extension, black oxide, installed at 150 ft-lb, pinned, and headspaced NOT INCLUDED Gas block (.625″), mi…
