CM7S 338 ARC Barreled Bolt Action – 12.5″
The Chattahoochee Munitions 338 ARC Barreled Bolt Action combines the CM7S Remington 700-footprint action with a compact 12.5-inch, 1:5 twist 338 ARC barrel. It provides the core assembly for a purpose-built bolt-action rifle while allowing the customer to select the stock or chassis, trigger, bottom metal, and other components for the finished firearm.
The 12.5-inch configuration is particularly interesting in 338 ARC. In Chattahoochee Munitions’ testing and loading experience with the configurations we have evaluated, much of the useful powder utilization occurs around the 12-inch range. The 12.5-inch barrel therefore provides a useful balance between cartridge efficiency and compact overall system length.
Combined with CM’s 1:5 twist specification, this 338 ARC Barreled Bolt Action is configured around our experience with heavy .338-caliber projectiles, including subsonic applications.
CM7S Action – Full PVD Coated
At the center of the barreled action is the Chattahoochee Munitions CM7S. The steel action uses the familiar Remington 700 footprint while incorporating a three-lug bolt, 60-degree bolt throw, integrated recoil lug, M16-style extractor, and features selected for a modern precision bolt-action platform.
- Remington 700 footprint
- 3-lug bolt design
- 60-degree bolt throw
- M16-style extractor
- One-piece .718″ diameter bolt body
- Wire EDM raceways
- Pinned 20 MOA Picatinny rail
- Large ejection port
- Lightweight action-body cutout
- .062″ firing pin
- Integrated .300″ recoil lug
- Tool-less fire-control removal
- Accepts Remington 700-pattern triggers
- 1-1/16″-16 barrel thread
- Side bolt-stop release
- Oversized bolt knob
- Spiral-fluted bolt
- Full PVD coating
- 25 oz action weight
12.5″ MÔS-Tek 338 ARC Barrel
The 338 ARC Barreled Bolt Action is fitted with a 12.5-inch stainless-steel barrel manufactured for Chattahoochee Munitions by MÔS-Tek. It uses 5R rifling and CM’s 1:5 twist specification and is finished in E100 Blackout Cerakote.
- 12.5″ barrel length
- 416R stainless steel
- 5R rifling
- 1:5 twist rate
- Shouldered crown
- 5/8×24 muzzle threads
- Remage barrel-nut system
- E100 Blackout Cerakote
Complete barreled-action weight: 57.4 oz / 3.59 lb
Weights and dimensions shown elsewhere in the product data may represent shipping dimensions rather than the physical dimensions of the barreled action.
Why CM Uses a 1:5 Twist
Chattahoochee Munitions specifies a 1:5 twist throughout the CM7S 338 ARC lineup. This differs from the 1:8 twist commonly associated with the standardized cartridge specification and is an intentional CM configuration.
CM has years of experience manufacturing and testing firearms using heavy .338-caliber projectiles. In our testing and experience, the faster twist has performed particularly well with heavy projectiles such as the 307-grain Hornady Sub-X.
For a 338 ARC Barreled Bolt Action intended to support heavy subsonic use, projectile stabilization is an important part of the overall system rather than an afterthought.
Why CM Offers a 12.5″ 338 ARC Barrel
Barrel length is one of the defining differences between the three CM7S 338 ARC barreled-action configurations.
In CM’s experience with the 338 ARC loads and configurations we have evaluated, much of the useful powder utilization occurs around the 12-inch range. That makes the 12.5-inch barrel a logical configuration for shooters who want to reduce overall firearm length without simply making the barrel as short as possible.
This becomes especially relevant when the finished rifle will be used with a suppressor. Reducing barrel length can offset some of the overall length added at the muzzle, producing a more compact complete system.
The 16-inch version remains available for customers who prefer a conventional rifle-length barrel, while the 8-inch CM7S configuration takes compactness considerably further.
338 ARC in a Compact Bolt-Action Platform
338 ARC is sized to operate within the AR-15 cartridge envelope, but the cartridge also presents interesting possibilities in a bolt-action firearm.
A manually operated action does not need to divert propellant gas to cycle the firearm. That removes the gas-system and buffer requirements associated with a semi-automatic platform and allows the finished rifle to be configured around a different set of priorities.
For customers interested in heavy subsonic ammunition, compact dimensions, and suppressor use, those characteristics make the 338 ARC Barreled Bolt Action a particularly useful starting point for a custom rifle.
6.5 Grendel Type II Bolt Face and AICS Magazine Architecture
The CM7S 338 ARC uses a 6.5 Grendel Type II .449″ bolt face. When installed in a compatible stock or chassis system, the finished rifle is designed around an AICS-pattern magazine architecture.
Chattahoochee Munitions has already tested and selected the magazine used with our complete CM7S rifles. The 338 ARC Bolt Action Magazine is a 10-round MDT polymer AICS-pattern magazine tested by CM with 338 ARC.
This testing is part of CM’s system approach to less-mainstream cartridges. Magazine selection is treated as a functional component of the firearm rather than something the customer should have to troubleshoot after completing a build.
Remage Architecture for a Custom Rifle Build
The CM7S 338 ARC Barreled Bolt Action uses a Remage barrel-nut system together with the Remington 700 action footprint.
This combination provides the customer with CM’s action and barrel configuration while preserving access to the extensive Remington 700 ecosystem for the remaining rifle components. The CM7S accepts Remington 700-pattern triggers and can be installed into compatible stocks or chassis systems.
For the shooter who wants to select those components independently, the barreled action provides the foundation without requiring the purchase of a complete CM7S firearm.
338 ARC Subsonic and Suppressed Applications
The combination of a 12.5-inch barrel, 1:5 twist, and manually operated action makes this configuration particularly relevant to shooters exploring the subsonic side of 338 ARC.
That does not mean barrel length or twist rate alone determines performance. Projectile construction, ammunition selection, suppressor configuration, and the intended application all remain important parts of the finished system.
The bolt-action platform does, however, remove the requirement for the ammunition to generate the gas necessary to operate a semi-automatic action. That gives the builder a different operating envelope when developing a compact suppressed rifle.
For a deeper technical discussion of the cartridge, including 1:8 versus 1:5 twist, barrel length, suppression, subsonic versus supersonic ammunition, and comparisons with 300 Blackout and 8.6 Blackout, read our 338 ARC Subsonic guide.
Three CM7S 338 ARC Barreled-Action Configurations
Chattahoochee Munitions offers three CM7S barreled-action configurations so customers can select the barrel length that makes sense for the intended finished rifle.
- 16″ – conventional rifle-length configuration
- 12.5″ – balance of compact dimensions and the powder-utilization characteristics observed in CM testing
- 8″ – maximum emphasis on compact system length
The same basic CM7S action architecture and 1:5 twist philosophy carry across all three configurations.
Explore Containment Zone 338
The 12.5-inch 338 ARC Barreled Bolt Action is one component of the larger Chattahoochee Munitions 338 ARC ecosystem.
CM offers the cartridge across CM7S bolt-action and CM15 AR-15 platforms, including complete firearms, barreled actions, upper receivers, and tested magazines. Explore the complete lineup in Containment Zone 338.
338 ARC Barreled Bolt Action FAQ
What is a 338 ARC Barreled Bolt Action?
The CM7S 338 ARC Barreled Bolt Action combines the CM7S Remington 700-footprint action with a chambered 338 ARC barrel and associated barrel hardware. It provides the core assembly around which a complete bolt-action rifle can be built.
Why does CM offer a 12.5″ 338 ARC barrel?
In Chattahoochee Munitions’ testing and loading experience with the configurations evaluated, much of the useful powder utilization occurs around the 12-inch range. The 12.5-inch configuration combines that characteristic with a substantially shorter barrel than a conventional 16-inch rifle.
What twist rate does the 12.5″ CM7S use?
The 12.5-inch CM7S uses a 1:5 twist. Chattahoochee Munitions uses this twist rate throughout its CM7S 338 ARC lineup based on our experience with heavy .338-caliber projectiles.
Does the CM7S use a Remington 700 footprint?
Yes. The CM7S uses a Remington 700 footprint and accepts Remington 700-pattern triggers, providing access to a broad ecosystem of compatible stocks, chassis systems, triggers, and related components.
What magazine system does the CM7S 338 ARC use?
The finished CM7S is designed around an AICS-pattern magazine system. Chattahoochee Munitions uses a tested 10-round MDT polymer magazine with its complete CM7S 338 ARC firearms.
Is the 12.5″ configuration intended for suppressed use?
The compact barrel length and bolt-action architecture make the 12.5-inch configuration particularly well suited as the foundation for a suppressed build. Suppressor selection, ammunition, projectile construction, and the complete rifle configuration still determine the performance of the finished system.
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