CM7S 300 Blackout Barreled Action – 8″

CM7S 300 BLK Short Barreled Action | 8″ 1:5 Twist

The CM7S 300 BLK Short Barreled Action combines the Chattahoochee Munitions CM7S action with an 8-inch Mos-Tek barrel to create the shortest barreled-action configuration in the Sector 300 bolt-action family. It provides a compact foundation for customers who want to select their own chassis, Remington 700-pattern trigger, magazine and rear configuration around a suppressed 300 Blackout system.

This is a purpose-manufactured bolt-action component—not an AR upper or a complete firearm. Its manually operated action eliminates gas-system and buffer-system variables, making the CM7S especially well suited to subsonic ammunition, suppression and minimum overall host length.

Visit Sector 300 to compare CM7S complete firearms, CM15 semi-automatic platforms, upper receivers, barreled actions and CM-vetted magazines within the Chattahoochee Munitions 300 Blackout ecosystem.

CM7S Remington 700-Footprint Action

The action at the center of this 300 BLK Short Barreled Action is manufactured by Chattahoochee Munitions. Its Remington 700 short-action footprint supports established chassis and trigger patterns while incorporating the proprietary features that define the CM7S platform.

• Remington 700 short-action footprint
• Three-lug bolt with a 60-degree lift
• One-piece .718″-diameter bolt body
• M16-style extractor
• Wire EDM-cut raceways for consistent tolerances and smooth bolt travel
• Integrated recoil lug
• Pinned 20 MOA Picatinny optic rail
• Large ejection port
• Lightened steel action body
• .062″ firing pin suitable for small-rifle-primer brass
• Tool-less fire-control removal
• Remington 700-pattern trigger compatibility
• 1-1/16″-16 barrel thread
• Side bolt-stop release
• Oversized bolt knob
• Spiral-fluted bolt
• Full PVD action and bolt coating
• Approximate bare action weight of 25 ounces

The full PVD coating provides a hard, corrosion-resistant surface across the action and bolt while supporting smooth manual operation. The three-lug architecture and 60-degree bolt lift also provide additional clearance around a mounted optic compared with a traditional two-lug action with a 90-degree lift.

8″ Mos-Tek 300 Blackout Barrel

The CM7S action is paired with an 8-inch barrel manufactured by Mos-Tek. Chattahoochee Munitions specifies a 1:5 twist throughout the CM7S 300 Blackout family, including this shortest configuration. The fast twist supports the stabilization requirements of the long, heavy projectiles commonly used in subsonic 300 Blackout ammunition.

• 8″ barrel length
• 416R stainless-steel construction
• 5R rifling
• 1:5 twist rate
• Shouldered crown
• 5/8×24 muzzle threads
• Remage barrel interface
• E100 Blackout Cerakote finish

The 5/8×24 muzzle thread accepts appropriately rated direct-thread suppressors and compatible muzzle devices. Any suppressor used with the 300 BLK Short Barreled Action must be rated by its manufacturer for 300 Blackout and an 8-inch barrel.

Minimum Host Length for a Suppressed System

The principal advantage of the 8-inch configuration is minimum host length. It is two inches shorter than the CM7S 10″ barreled action and four and a half inches shorter than the 12.5″ version. That reduction becomes especially meaningful after a suppressor is attached to the muzzle.

The 8-inch barrel should not be confused with CM’s optimal 10–10.5″ barrel-length recommendation for overall 300 Blackout performance. This 300 BLK Short Barreled Action prioritizes compactness. Customers who have room for a slightly longer host should also consider the CM7S 10″ 300 Blackout barreled action.

The manually operated action also means that ammunition does not need to produce sufficient pressure to cycle a bolt carrier. There is no gas port, gas block, gas tube, buffer or recoil spring to tune. This allows ammunition selection to be approached independently from the operating requirements of a semi-automatic firearm.

Designed Around Suppressed Subsonic Use

Chattahoochee Munitions considers suppressed subsonic performance the central purpose of 300 Blackout. The short barrel helps control the overall length of the system after a suppressor is installed, while the 1:5 twist provides the rotational speed needed to support long subsonic projectiles at relatively low velocities.

A bolt action also keeps the breech closed until the shooter manually cycles it. This avoids action noise during the shot and eliminates the receiver gas and ejection-port noise associated with a cycling semi-automatic platform. These characteristics make the CM7S 300 BLK Short Barreled Action a focused foundation for a compact suppressed system.

Subsonic and supersonic ammunition can both be used, but individual loads can produce different velocities, points of impact and terminal results. Projectile construction and stability should be verified with the intended barrel, ammunition and suppressor combination before that combination is relied upon for a particular application.

For a detailed discussion of barrel length, twist rate, suppressor behavior, projectile selection and the operating differences between CM7S and CM15 firearms, read the 300 Blackout Subsonic Guide.

Complete the CM7S System

The barreled-action format allows customers to select the remaining components around their intended use. Completing the system requires an appropriate short-action chassis or stock, a Remington 700-pattern trigger, compatible rear components and a suitable magazine system.

Magazine selection is particularly important with 300 Blackout. Chattahoochee Munitions has tested and recommends the CM-vetted 300 Blackout bolt-action magazine for CM7S 300 Blackout firearms equipped with compatible AICS-pattern bottom metal.

CM7S 300 BLK Short Barreled Action Specifications

Manufacturer	Chattahoochee Munitions
Platform	CM7S bolt action
Caliber	300 AAC Blackout / 300 BLK
Configuration	Barreled action
Action Footprint	Remington 700 short action
Bolt	Three lug, 60-degree lift, one-piece .718″ body
Extractor	M16 style
Recoil Lug	Integrated
Action Finish	Full PVD coating
Optic Rail	Pinned 20 MOA Picatinny
Trigger Compatibility	Remington 700 pattern
Barrel Manufacturer	Mos-Tek
Barrel Length	8″
Barrel Material	416R stainless steel
Rifling	5R
Twist Rate	1:5
Crown	Shouldered crown
Muzzle Thread	5/8×24
Barrel Interface	Remage
Barrel Finish	E100 Blackout Cerakote
Barreled Action Weight	49.21 oz / 3.07 lb

The weight and dimensions displayed in the Additional Information tab are shipping values and should not be interpreted as the physical specifications of the barreled action.

300 BLK Short Barreled Action FAQ

What is included with this product?

The product includes the CM7S action and installed 8-inch Mos-Tek 300 Blackout barrel. The chassis or stock, trigger, magazine and other completion components are selected separately.

Does the CM7S barreled action have a gas system?

No. The CM7S is a manually operated bolt action. It does not use a gas block, gas tube, buffer or other semi-automatic operating components.

Why does the 8″ barrel use a 1:5 twist?

The 1:5 twist provides increased rotational speed for stabilizing the long, heavy projectiles commonly used in subsonic 300 Blackout ammunition. CM uses a 1:5 twist throughout the CM7S 300 Blackout family.

Is 8″ CM’s optimal 300 Blackout barrel length?

No. CM considers approximately 10–10.5 inches the optimal general-purpose barrel length under its subsonic-first 300 Blackout philosophy. The 8″ configuration is offered for customers who place a higher priority on minimum host length.

Can the barreled action use subsonic and supersonic ammunition?

Yes. Because it is manually operated, the action does not depend on ammunition pressure to cycle. Projectile stability, velocity, point of impact and terminal performance can still vary among individual loads.

Is this a complete firearm?

No. This product is a barreled action. Customers seeking a finished CM-manufactured firearm can compare complete CM7S configurations through Sector 300.