.308 Winchester, By the Numbers
Winchester introduced the .308 in 1952 from Frankford Arsenal’s T65 experiments, two years before NATO adopted its military twin, the 7.62x51. It is the most widely used short-action big-game cartridge in the world and the round the AR-10 was designed for: a 150 to 180 gr .308″ bullet at 2,600 to 2,800 fps, 2,600 to 2,800 ft-lb at the muzzle, loaded to a SAAMI maximum of 62,000 psi. It takes deer, elk, and black bear at any reasonable range and holds supersonic past 900 yards with match bullets.
Barrel length costs it less than most shooters think. Hornady publishes its 168 gr ELD Match at 2,700 fps from a 24″ barrel; the .308 loses roughly 20 to 25 fps per inch, so a 20″ runs about 2,600, an 18″ about 2,550, a 16″ about 2,500, and even the 13.9″ is a 2,450 fps .308, which is more than any 6.5 Grendel or 300 Blackout will ever be. What the short barrels give up is the velocity to keep a match bullet supersonic at extreme range; what they gain is an AR-10 that handles like an AR-15.
Faxon rifles every Duty Series .308 at 1:10, the twist that stabilizes 150 through 178 gr bullets, and cuts them on two contours: the AR-10 Gunner (formerly Big Gunner), with a .750″ body and the balance that made it Faxon’s signature AR-10 barrel, and the Pencil, the lightest .308 AR barrel Faxon makes. The 13.9″ and 16″ run mid-length gas; the 18″ and 20″ run rifle-length. All are headspaced on a DPMS Gen 1 / LR-308 extension with a .308 go/no-go gauge.
Manufacturer-published factory data — 24″ test barrel where stated
| Load | Bullet | Muzzle velocity | Muzzle energy | Test barrel |
| Hornady Match | 168 gr ELD Match | 2,700 fps | 2,719 ft-lb | 24″ |
| Federal Fusion | 150 gr bonded SP | 2,820 fps | 2,648 ft-lb | not stated |
| Federal Gold Medal | 175 gr Sierra MatchKing | 2,600 fps | 2,627 ft-lb | not stated |
Sources: Hornady and Federal product pages. The .308 loses roughly 20–25 fps per inch of barrel below 24″: about 100 fps at 20″, 150 at 18″, 200 at 16″, 250 at 13.9″. Estimates, not Faxon chronograph figures.
Duty Series .308 Winchester Barrels
All 1:10 twist, 4150 CMV, QPQ nitride inside and out, 5/8x24 muzzle. Weights are nominal; prices are MSRP.
What You Need to Build It
A DPMS Gen 1 / LR-308-pattern upper receiver and .308 bolt carrier group (the extension is DPMS-pattern; Armalite AR-10-pattern uppers are different), a DPMS-pattern barrel nut, SR-25/DPMS-pattern magazines, and a rifle or carbine buffer system matched to the receiver set. Every barrel takes a .750″ gas block on a 1.9″ journal; the 13.9″ and 16″ take a mid-length gas tube and the 18″ and 20″ a rifle-length tube. Muzzle is 5/8x24, the .30-caliber standard, so any .30-cal device or suppressor fits.
What Every Duty Series Barrel Shares
Duty Series is Faxon’s 4150 CMV line: the M4/M16 barrel alloy, button rifled, stress relieved, and salt-bath QPQ nitrided inside the bore and out, which hardens the surface while adding virtually nothing to it, roughly a tenth the width of a human hair, and leaves no plated layer to wear through. Every barrel is turned, crowned at 11°, chambered, 100% wet magnetic-particle inspected, and nitrided, then has its gas port drilled and reamed and its extension torqued to 150 ft-lb, pinned, and headspaced with a go/no-go gauge, and is laser-engraved with the Faxon shield, order number, and cartridge and twist, in Faxon’s Greater Cincinnati, Ohio plant. Faxon’s AR-15 and AR-10 barrels have been voted Favorite Aftermarket Barrel by Shooting Sports Retailer every year since 2022. All Duty Series barrels › All rifle barrels ›
Duty Series .308 Winchester FAQs
Which AR-10 pattern do these barrels fit?
DPMS Gen 1 / LR-308 pattern, which is the common commercial AR-10 pattern: DPMS, Aero Precision M5, and most others. They are not for the Armalite AR-10 pattern. Faxon’s own AR-10 receiver sets are DPMS-pattern.
Why are Faxon .308 barrels so light?
Because a .308 AR barrel does not need to be three pounds. The AR-10 Gunner (formerly Big Gunner) puts its steel behind the gas block and runs a .750″ body ahead of it, and the Pencil takes that further; a 16″ Gunner is 1.91 lb and a 16″ Pencil 1.83. The rifle handles like an AR-15 and still shoots like a .308.
Is 1:10 twist right for 175 gr match bullets?
Yes. 1:10 is the standard .308 twist and stabilizes 150 through 178 gr bullets, including the 168 and 175 gr match loads, at any length in the line.
Which length for a hunting rifle? For a DMR?
For hunting, the 16″ or 18″: a 16″ .308 is still a 2,500 fps .308 and the rifle carries easily. For a designated-marksman or long-range rifle, the 20″ on rifle-length gas gives the most velocity and the softest cycling. The 13.9″ is for a compact rifle with a permanently attached device.
Ballistics are manufacturer-published figures from the test barrels stated; velocity estimates for other lengths are approximations, not Faxon chronograph data. Dimensions are from Faxon engineering prints; weights are nominal. Prices are MSRP. Check your state’s hunting regulations before choosing a cartridge.
