FAXON COMBAT SERIES MED TAPER 12.5" CARBINE-LENGTH 5.56 NATO AR15 BARREL

Rifle Barrels › Combat Series › 5.56 NATO / .223 Remington › 12.5″ Medium Taper  |  Works with: .750″ gas block • carbine gas tube • 5.56/300 BLK BCG • 1/2x28 muzzle devices

Why Chrome-Lined

The Combat Series is Faxon’s classic-configuration line. It shares the Duty Series’ 4150 CMV steel and build process, but instead of nitride it uses a hard chrome-lined bore and chamber with a manganese phosphate exterior, the way military carbine barrels have been made for decades. Chrome lining resists corrosion and the throat erosion that comes with heat and high round counts, which is why it is still the traditional choice for sustained full-auto fire and hard-use duty rifles.

Chrome lining still has its place, mainly sustained automatic fire, but for the vast majority of shooters Faxon’s salt-bath nitride does what they need and more. If you don’t need chrome, see the Duty Series: the same 4150 CMV, salt-bath QPQ nitrided inside and out.

The 12.5″ Medium Taper Profile and Carbine-Length Gas

The Medium Taper sits between a Pencil and a Government contour: more steel than a lightweight barrel for heat and hard use, with a taper that keeps a short carbine quick to handle. Carbine-length gas is the standard military system for 14.5″ and 16″ carbines and short 5.56 barrels. It is proven, parts are everywhere, and it cycles reliably across a wide range of ammunition.

The 5.56 NATO chamber runs both 5.56 NATO and .223 Remington, and the 1:7 twist is the military standard: it stabilizes 55 gr through 77 gr bullets, including heavy match and duty loads.

Legal note: a 12.5″ barrel makes the firearm an AR pistol or a short-barreled rifle, depending on how it is configured. Know and follow federal, state, and local laws before you build.

How It’s Made

1. Drill and ream: 4150 CMV bar gun-drilled and reamed
2. Button rifle: 1:7 twist, 6-groove button rifling
3. Air gauge: Bore air gauged
4. Stress relieve: Stress relieved after rifling
5. Profile and thread: Medium Taper profile, .750″ gas journal, 1/2x28 muzzle threads, and target crown
6. Chamber: 5.56 NATO chamber cut
7. MPI: 100% wet magnetic particle inspected
8. Chrome line: Bore and chamber hard chrome-lined
9. Port and extension: Gas port drilled; M4 extension torqued, pinned, and headspaced
10. Phosphate: Manganese phosphate exterior
11. Engrave and inspect: Laser-engraved, then final inspected

How We Inspect It

Faxon barrels are built to a written control plan, and each run is logged on inspection sheets. Here is what this barrel goes through before it ships.

What’s in the Box

What Owners Say

This barrel doesn’t have reviews on FaxonFirearms.com yet. If you own one, tell other shooters how it runs in the review section below.

Build It Out

Compare Your Options

See every barrel in this line on the Combat Series page.

Combat Series 12.5″ Medium Taper FAQs

Is the bore chrome-lined?

Yes. The bore and chamber are hard chrome-lined, and the exterior is manganese phosphate.

How is the Combat Series different from the Duty Series?

Both are 4150 CMV and button rifled. Combat Series barrels use a chrome-lined bore and manganese phosphate exterior in classic configurations; Duty Series barrels are salt-bath QPQ nitrided inside and out. Chrome is the traditional choice for sustained full-auto fire; for most shooters, nitride does what they need and more.

What comes with the barrel?

The barrel with its M4 extension installed, torqued, pinned, and headspaced. The gas block, gas tube, and muzzle device are sold separately.

What gas block does it take?

A .750″ low-profile gas block on the 1.9″ journal. Faxon’s patented adjustable .750″ gas block is recommended for suppressed builds and lightweight carriers.

Can I run a suppressor?

Yes. The muzzle is threaded 1/2x28. Use a 5.56 or larger suppressor, and consider an adjustable gas block to tune for it.

What ammunition does the 1:7 twist like?

The 1:7 twist stabilizes 55 gr through 77 gr 5.56 NATO and .223 Remington bullets, including heavy match and duty loads.

Is it full-auto capable, and how much heat can it take?

Yes. Combat Series barrels are full-auto capable, and a chrome-lined bore is the traditional choice for sustained automatic fire: the hard chrome lining resists heat-driven throat erosion. Each barrel is stress relieved and magnetic particle inspected for flaws. What limits any barrel on automatic fire is heat. A good guideline, drawn from U.S. military guidance for the M4 carbine: about 12 to 15 rounds a minute can be fired indefinitely, and continuous rapid fire should stop at about 150 rounds so the barrel can cool. Short barrels heat up faster than a 16″ rifle barrel, so expect to reach those limits sooner. Push past that and wear speeds up, which shortens barrel life. If the barrel smokes or starts to glow, stop; military testing has seen M4 barrels fail at about 1,360°F. A hot chamber can cook off a round in as little as 10 seconds, so clear it quickly or keep it pointed in a safe direction. And heat affects accuracy in every barrel: groups open up as it heats. Faxon’s stress relieving keeps point of impact from walking, but let it cool before you check zero or shoot for groups.

Where is it made?

In Greater Cincinnati, Ohio, and it is covered by the Faxon Lifetime Guarantee.

Full-auto heat guidance is general, based on published U.S. military rate-of-fire guidance, not Faxon testing; barrel life under automatic fire depends on rate of fire, ammunition, and cooling. HARMONIX® and MuzzLok® are trademarks of Faxon Firearms. Know and follow all federal, state, and local laws.