8.6 Blackout, By the Numbers
8.6 Blackout was designed by Q, LLC, under Kevin Brittingham, and reached production in 2022; SAAMI accepted it in January 2026 at 62,000 psi. It is a .308 Winchester case shortened to about 1.685″ and necked up to .338″, so it runs in a standard AR-10 bolt and magazine and in short-action bolt guns with a barrel change, and it was built subsonic-first: a 285 to 342 gr bullet at about 1,000 to 1,050 fps, suppressed, with the 200 to 210 gr supersonics at 1,950 to 2,100 fps from a 12″ barrel as the second act.
The twist is what makes it work. A 1:3 barrel spins a subsonic bullet at roughly 240,000 rpm, more than four times what a 1:10 .308 does at the same speed, and that rotational energy is what makes a 1,000 fps copper bullet open up and wound like a much faster one; Q called it the blender effect. The SAAMI reference drawing lists a 1:6 twist and Faxon has built 8.6 barrels at both 1:6 and 1:3; the Duty Series barrels here are Faxon’s original 1:3, the twist the cartridge was designed around, which Faxon was the first to button-rifle successfully at production scale.
All three barrels are the AR-10 Gunner contour with an .875″ × 1.9″ gas journal, pistol gas on the 8″ and 12″ and carbine gas on the 16″, and Q’s M18x1.5 muzzle with the tapered shoulder that seats a taper-mount suppressor; the taper adapter that lets a standard 5/8x24 device thread on is included. Ammunition makers publish 8.6 figures from 12″ and 16″ barrels, which is why those lengths are here; the 8″ gives up little on subsonics and a few hundred fps on supersonics. Faxon’s 8.6 Blackout guide covers loads, twist, and builds in depth.
Gorilla Ammunition factory data — 12″ and 16″ test barrels
| Load | Bullet | Muzzle velocity | Test barrel |
| Gorilla 8.6 BLK Supersonic | 210 gr Barnes TSX | 2,040 fps | 12″ |
| Gorilla Silverback Subsonic | 285 gr fracturing copper | 1,050 fps | 16″ |
| Gorilla Pork Shredder Subsonic | 342 gr expanding copper | 1,000 fps | 12″ |
Source: Gorilla Ammunition product pages; Gorilla does not publish muzzle energy (the 210 gr at 2,040 fps works out to roughly 1,940 ft-lb, the 342 gr at 1,000 fps to roughly 760). Gorilla ties the 210 gr figure to current production lots. From the 8″ expect subsonics within about 50 fps and supersonics 200–300 fps lower; estimates, not Faxon chronograph figures.
Duty Series 8.6 Blackout Barrels
All 1:3 twist, 4150 CMV, QPQ nitride inside and out, M18x1.5 taper muzzle. Weights are nominal; prices are MSRP.
What You Need to Build It
A DPMS Gen 1 / LR-308-pattern upper receiver, .308 bolt carrier group, and barrel nut; SR-25/DPMS-pattern .308 magazines feed it. All three barrels take an .875″ gas block on a 1.9″ journal; the 8″ and 12″ take a pistol-length gas tube and the 16″ a carbine-length tube. The adjustable block is the tool for running heavy subsonics suppressed and supersonics unsuppressed from one barrel. The muzzle is M18x1.5 with a tapered shoulder for a taper-mount suppressor; the included adapter converts it to 5/8x24 for a standard .338-capable device or HUB mount.
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 8.6 Blackout FAQs
Why 1:3 twist?
Because 8.6 Blackout was designed around it. The cartridge’s subsonic loads rely on rotational energy, not velocity, to make a bullet expand: a 1:3 barrel spins a 1,000 fps bullet at about 240,000 rpm, and that spin is what opens a copper subsonic and makes it wound like a far faster cartridge. Faxon was the first to button-rifle a 1:3 barrel for the cartridge at production scale. The SAAMI drawing lists 1:6, and Faxon has built both; these barrels are 1:3.
What bolt, upper, and magazines does it use?
A standard DPMS-pattern .308 bolt carrier group, upper, and barrel nut, and SR-25/DPMS-pattern .308 magazines; the 8.6 case is a shortened .308 case with the same .473″ head. Only the barrel changes on an AR-10.
What is the M18x1.5 taper muzzle, and what fits it?
Q’s muzzle standard for 8.6 Blackout: M18x1.5 threads behind a tapered shoulder that centers and locks a taper-mount suppressor. Every Faxon 8.6 barrel ships with a taper adapter that converts it to 5/8x24, so a standard .338-capable muzzle device or a HUB-mount suppressor threads on.
Which length?
The 12″ is the length the cartridge was designed around and the one most ammunition is tested in. The 8″ gives up little on subsonics and is the smallest, quietest 8.6 pistol or SBR. The 16″ is a rifle with no paperwork and the fastest with supersonics. Subsonics perform nearly the same from all three.
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.
