8.6 Blackout Rifles, Pistols and SBRs

8.6 blackout rifle

Area 8.6: 8.6 Blackout Bolt Action and AR10 Firearms

8.6 Blackout is a .338-caliber cartridge made from the 6.5 Creedmoor case for heavy subsonic bullets from short, suppressed firearms. Its 300 to 352 gr subsonic bullets carry roughly 680 to 840 ft-lb at about 1,000 fps, and SAAMI standardized the cartridge in January 2026.

Chattahoochee Munitions manufactures complete 8.6 Blackout firearms on two platforms: the CM7S bolt action as 8-inch and 12.5-inch pistols or SBRs and 16-inch rifles, plus 12.5-inch and 16-inch models with walnut WOOX furniture; and the CM10 AR10 as 8-inch and 12.5-inch pistols or SBRs and 16-inch rifles. Every 8.6 Blackout firearm is offered with a 1:3 or 1:5 twist Mos-Tek barrel. It also manufactures CM7S barreled actions and supplies vetted magazines for both platforms. Chattahoochee Munitions has worked with the cartridge for more than four years, since before SAAMI standardization.

New to the cartridge? Start with What Is 8.6 Blackout?, 8.6 Blackout subsonic or 375 Raptor vs 8.6 Blackout.

CM7S Bolt Action Rifles

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CM10 Semi-Auto Rifles, Pistols, SBRs

Barreled Actions

  • 8.6 barreled action Select options

    Barreled Actions

    CM7S 8.6 Blackout 16″ Barreled Action

     $1,768.98 Select options This product has multiple variants. The options may be chosen on the product page
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    Barreled Actions

    CM7S 8.6 Blackout 12.5″ Barreled Action

     $1,718.98 Select options This product has multiple variants. The options may be chosen on the product page
  • 8.6 BLK Barreled Action Select options

    Barreled Actions

    CM7S 8.6 Blackout 8″ Barreled Action

     $1,718.98 Select options This product has multiple variants. The options may be chosen on the product page

Magazines

Overrun Barrels - Limited Time

CM Gear

What Is 8.6 Blackout?

8.6 Blackout (8.6 BLK) is a .338-caliber rifle cartridge made from the 6.5 Creedmoor case, shortened and necked up to hold .338-inch bullets. It keeps the .308 Winchester family case head, so it uses a standard .308 bolt face and .308-length magazines, and it needs an AR10 or a short-action bolt action. Very fast rifling stabilizes long, heavy bullets at subsonic speed. SAAMI issued the 8.6 BLACKOUT standard on January 19, 2026, and revised it on April 7, 2026. Read What Is 8.6 Blackout?

8.6 Blackout Specifications at a Glance

  • Bullet diameter: .338 inch (8.6 mm)
  • Case: 1.685 inches, from the 6.5 Creedmoor (.308 Winchester family)
  • Cartridge overall length: 2.560 to 2.810 inches
  • Bolt face: .308 Winchester
  • Pressure: 62,000 psi maximum average (SAAMI)
  • SAAMI reference load: 200 gr at 2,200 fps, 16-inch test barrel with a 1:6 twist
  • Subsonic loads: 300 to 352 gr at about 950 to 1,050 fps, roughly 680 to 840 ft-lb
  • Chattahoochee Munitions twist: 1:3 or 1:5 on every 8.6 Blackout firearm
  • Chattahoochee Munitions barrels: Mos-Tek, 416R stainless, 5R rifling, E100 Blackout Cerakote

Pressure, reference load and dimensions are from SAAMI cartridge and chamber drawings.

8.6 Blackout Subsonic: Heavy Bullets, Short Barrels, Suppressors

Short-barrel subsonic shooting is the heart of Area 8.6. Below the speed of sound there is no ballistic crack, so a suppressor only has to reduce muzzle blast, and energy comes from bullet weight. That is where the 8.6 Blackout’s 300 to 352 gr bullets earn their place. In Chattahoochee Munitions testing, powder use with 8.6 Blackout subsonic loads is effectively complete at about 12 to 12.5 inches, so the 12.5-inch CM7S, in the CM7 chassis or with walnut WOOX furniture, and the 12.5-inch CM10 sit at the center of the lineup, with 8-inch models for a shorter package and 16-inch models for supersonic loads and no SBR paperwork. See 8.6 Blackout subsonic and 8.6 Blackout barrel length.

1:3 or 1:5 Twist?

Chattahoochee Munitions offers both because its testing does not support one twist for every load. With barrels of about 12.5 inches or longer, testing has generally favored 1:5 for bullets of about 300 gr and under, and 1:3 for heavy subsonic bullets of about 323 gr and up. These are practical guidelines, not universal ballistic rules; bullet length and construction, velocity and barrel length all affect stability. SAAMI’s test barrel uses 1:6. See 8.6 Blackout twist rate.

CM7S 8.6 Blackout Bolt Action

The CM7S is manually operated, so it adds no action noise when suppressed and cycles any subsonic or supersonic load by hand. Chattahoochee Munitions manufactures it with the Remington 700 footprint, a three-lug bolt with a 60-degree throw and an M16-style extractor, an integrated recoil lug, a pinned 20 MOA rail, a Mos-Tek 416R stainless barrel with E100 Blackout Cerakote, and a TriggerTech trigger. It feeds from a vetted 10-round AICS-pattern magazine. The CM7S 8.6 Blackout is offered at 8, 12.5 and 16 inches in the CM7 chassis, at 12.5 and 16 inches with walnut WOOX furniture, and as 8, 12.5 and 16-inch barreled actions.

CM10 8.6 Blackout AR10

The CM10 8.6 Blackout uses conventional AR10/SR-25-pattern architecture, unlike the center-feed CM10 configurations Chattahoochee Munitions developed for 375 Raptor and 458 SOCOM XL. Long .338 bullets need more than a chambered barrel, so the CM10 8.6 Blackout has customized feed ramps, vetted 10 and 20-round SR25-pattern magazines, a Superlative Arms adjustable gas block and an ODIN Works AR10 adjustable buffer, so it can be tuned for heavy subsonic or supersonic ammunition. It uses a TriggerTech Duty trigger (straight, curved or two-stage straight) and is offered at 8, 12.5 and 16 inches. See 8.6 Blackout bolt action vs semi auto.

Suppressors for 8.6 Blackout

Use a suppressor rated for .338 caliber or larger. The CM7S bolt action always gets an enclosed suppressor. On the CM10, use an enclosed suppressor with subsonic ammunition; with supersonic ammunition a flow-through suppressor is recommended. In Chattahoochee Munitions testing, steel suppressors have generally provided better sound reduction than titanium suppressors of similar volume, while titanium saves weight. The PLACID 375 is an enclosed suppressor rated from 5.56 NATO through .375. A suppressed firearm is still not hearing safe; see the NIOSH noise guidance and 8.6 Blackout suppressor.

8.6 Blackout Ammunition

Chattahoochee Munitions manufactures the firearms; factory 8.6 Blackout ammunition comes from specialty makers. Just Cause USA lists 350 and 352 gr Maker REX subsonic loads and a 180 gr supersonic load. Black Butterfly Ammunition lists 305 and 352 gr subsonic loads in bolt action and AR10 versions, tested in a 12.5-inch, 1:3 Chattahoochee Munitions firearm at about 1,000 fps. See 8.6 Blackout ammo, 8.6 Blackout ballistics and 8.6 Blackout hunting.

Compare 8.6 Blackout

8.6 Blackout Guides

8.6 Blackout FAQ

What is 8.6 Blackout?

A .338-caliber cartridge made from the 6.5 Creedmoor case for heavy subsonic bullets from short, suppressed firearms. SAAMI standardized it in 2026.

Who makes 8.6 Blackout rifles?

Chattahoochee Munitions manufactures complete 8.6 Blackout firearms: the CM7S bolt action at 8, 12.5 and 16 inches in the CM7 chassis and at 12.5 and 16 inches with walnut WOOX furniture, and the CM10 AR10 at 8, 12.5 and 16 inches, each with a 1:3 or 1:5 twist Mos-Tek barrel.

Who makes an 8.6 Blackout bolt action?

Chattahoochee Munitions manufactures the CM7S 8.6 Blackout bolt action as a pistol, SBR or rifle, and as a barreled action with the Remington 700 footprint.

Who makes an 8.6 Blackout AR10?

Chattahoochee Munitions manufactures the CM10 8.6 Blackout AR10 at 8, 12.5 and 16 inches, with customized feed ramps, an adjustable gas block and an adjustable buffer.

Does Chattahoochee Munitions offer 1:3 and 1:5 twist?

Yes, on every 8.6 Blackout firearm and barreled action. With barrels of about 12.5 inches or longer, testing has generally favored 1:3 for bullets of about 323 gr and up and 1:5 for about 300 gr and under.

What barrel length suits 8.6 Blackout subsonic?

About 12 to 12.5 inches. In Chattahoochee Munitions testing, powder use with subsonic loads is effectively complete in that range.

Can 8.6 Blackout run in an AR15?

No. It needs an AR10 such as the CM10 or a short bolt action such as the CM7S.

Does Chattahoochee Munitions test magazines for 8.6 Blackout?

Yes. Chattahoochee Munitions vets the magazines it supplies with both the CM7S and the CM10, so magazine selection is part of the complete firearm.

What suppressor fits 8.6 Blackout?

One rated for .338 or larger, such as the PLACID 375. Use an enclosed suppressor on the CM7S, and on the CM10 with subsonic ammunition.

Does Chattahoochee Munitions sell 8.6 Blackout ammunition?

No. Factory ammunition is available from makers such as Just Cause USA and Black Butterfly Ammunition.

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