CM7S 300 Blackout Barreled Action – 12.5”

300 Blackout Barreled Action | CM7S 12.5″ 1:5 Twist

The 300 Blackout Barreled Action combines the Chattahoochee Munitions CM7S action with a 12.5-inch Mos-Tek barrel for customers who prefer a longer bolt-action configuration while retaining the suppressor-ready architecture of the Sector 300 family. It provides the central action and barrel components while allowing the customer to select the chassis, Remington 700-pattern trigger, magazine and rear configuration separately.

This is a purpose-manufactured bolt-action component—not an AR upper or a complete firearm. Its manually operated action eliminates the gas-system and buffer-system variables associated with a semi-automatic platform, allowing ammunition and suppressor selection to be approached independently from the pressure required to cycle an action.

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 Blackout Barreled Action is manufactured by Chattahoochee Munitions. Its Remington 700 short-action footprint provides compatibility with established chassis and trigger patterns while incorporating the proprietary architecture of 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 design produces a 60-degree bolt lift, providing additional clearance around a mounted optic compared with a traditional two-lug action with a 90-degree lift.

12.5″ Mos-Tek 300 Blackout Barrel

The CM7S action is paired with a 12.5-inch barrel manufactured by Mos-Tek. Chattahoochee Munitions specifies a 1:5 twist throughout the CM7S 300 Blackout family. The fast twist supports the stabilization requirements of the long, heavy projectiles commonly used in subsonic ammunition.

• 12.5″ 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 installed on the 300 Blackout Barreled Action must be rated by its manufacturer for the cartridge, projectile and barrel length being used.

Why Choose the 12.5″ Configuration?

The 12.5-inch model is the longest of the current CM7S 300 Blackout barreled-action configurations. It is intended for customers who prefer a longer physical profile, additional muzzle clearance beyond a chassis or forend, and the balance characteristics of a longer barrel.

Chattahoochee Munitions does not position 12.5 inches as the optimal barrel length for extracting additional 300 Blackout velocity. CM considers approximately 10–10.5 inches the optimal range under its subsonic-first philosophy, with substantially complete powder burn occurring at approximately 9–10.5 inches. The additional barrel length should therefore be selected for configuration, handling and component-fit considerations—not a manufactured claim of superior ballistic performance.

Customers seeking CM’s preferred overall barrel-length balance can compare the 10″ 300 Blackout bolt action. Those prioritizing minimum suppressor-host length can compare the 8″ 300 BLK short barreled action.

Designed Around Suppressed Subsonic Use

Chattahoochee Munitions considers suppressed subsonic operation the defining use of 300 Blackout. Although supersonic ammunition can be used, other cartridges offer stronger dedicated supersonic performance. The central advantage of 300 BLK is its ability to launch long, heavy projectiles below the speed of sound from a compact, suppressor-ready platform.

The manually operated 300 Blackout Barreled Action keeps the breech closed until the shooter cycles the bolt. It therefore avoids the action noise, ejection-port noise and receiver gas associated with a cycling semi-automatic firearm. This makes the CM7S a focused option for customers developing a suppressed bolt-action system.

Subsonic and supersonic loads can produce different velocities, trajectories, points of impact and terminal results. Even two loads within the same subsonic category may behave differently because of changes in projectile construction, weight, length and velocity. Every ammunition-and-suppressor combination should be evaluated before being relied upon for a particular application.

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

1:5 Twist for Heavy Subsonic Projectiles

The 1:5 twist increases rotational speed compared with a conventional 1:7 twist. This is particularly valuable with the long, heavy projectiles commonly loaded in subsonic 300 Blackout ammunition. CM uses a 1:5 twist throughout the CM7S 300 Blackout family rather than changing twist rates among the 8-inch, 10-inch and 12.5-inch configurations.

Twist rate does not replace responsible ammunition evaluation. Projectile length, construction, weight and actual muzzle velocity all affect stabilization. Shooters should confirm projectile stability before installing a suppressor and repeat that evaluation whenever changing to a materially different load.

Bolt-Action Suppressor Advantages

A manually operated action does not require ammunition pressure to unlock and cycle the firearm. There is no gas port, gas block, gas tube, buffer or recoil spring to tune when changing between subsonic loads, supersonic loads or suppressors.

The closed action also keeps combustion gas contained until the shooter manually opens the bolt. This produces a different suppressed experience from a semi-automatic platform, where some sound and gas escape through the ejection port during cycling.

These operating characteristics do not make every load perform identically. Ammunition selection still affects velocity, consistency, projectile stability, point of impact and terminal behavior. The advantage is that those differences do not need to be balanced against the pressure required to operate a semi-automatic action.

Complete the 300 Blackout Barreled Action System

The barreled-action format gives the customer control over the remaining system components. Completion 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 firearms equipped with compatible AICS-pattern bottom metal.

Customers who prefer a complete firearm manufactured by Chattahoochee Munitions can use Sector 300 to compare finished CM7S configurations rather than selecting the chassis, trigger, magazine and rear components individually.

300 Blackout 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	12.5″
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	57.4 oz / 3.59 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 Blackout Barreled Action FAQ

What is included with this product?

The product includes the CM7S action and installed 12.5-inch Mos-Tek 300 Blackout barrel. The chassis or stock, trigger, magazine and other completion components are selected separately.

Is this a complete firearm?

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

Does this barreled action use 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 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 this twist throughout the CM7S 300 Blackout family.

Does the 12.5″ barrel produce more useful velocity than the 10″ model?

CM does not position the 12.5″ configuration around a meaningful velocity advantage. The longer barrel is offered for customers who prefer its physical profile, balance, muzzle clearance or component compatibility.

Can it use both subsonic and supersonic ammunition?

Yes. The manually operated action does not rely on ammunition pressure to cycle. Projectile stability, velocity, point of impact and terminal performance can still vary among individual loads and should be evaluated accordingly.