CM7S 338 ARC SBR – 8″ FDE Metallic
The CM7S 338 ARC SBR is the most compact end of the Chattahoochee Munitions bolt-action 338 ARC platform. Built around an 8-inch MÔS-Tek 1:5 twist barrel, PVD-coated CM7S action, TriggerTech Primary trigger, and billet CM7 chassis, this configuration prioritizes minimum overall length while retaining the features of a precision bolt-action system.
At approximately 5 pounds 12 ounces and as little as 20.5 inches overall depending on configuration, the 8-inch CM7S creates an exceptionally compact .338-caliber platform. This version features an FDE Metallic Cerakote chassis and can be configured as an SBR with a telescoping buttpad or as a pistol with a telescoping Tailhook brace.
Chattahoochee Munitions has extensive experience manufacturing and testing heavy .338-caliber firearm systems. The 8-inch configuration deliberately prioritizes compactness over the greater powder utilization available from our longer 338 ARC barrels.
CM7S Bolt Action – Full PVD Coating
The foundation of the 338 ARC SBR is the Chattahoochee Munitions CM7S action. Built around the Remington 700 footprint, the CM7S incorporates features selected for precision, hunting, and field use.
- Remington 700 footprint
- Three-lug bolt design
- 60-degree bolt throw
- M16-style extractor
- One-piece .718″ diameter bolt body
- Wire EDM raceways for consistent tolerances and smooth cycling
- Pinned 20 MOA Picatinny rail
- Large ejection port
- Lightweight action-body cutout
- .062″ firing pin
- Integrated .300″ recoil lug
- Tool-less fire-control removal
- Compatible with Remington 700-pattern triggers
- 1-1/16″-16 barrel thread
- Side bolt-stop release
- Oversize bolt knob
- Spiral-fluted bolt
- Full PVD coating
- 25 oz action weight
8″ MÔS-Tek 338 ARC Barrel – 1:5 Twist
The CM7S uses a MÔS-Tek custom bolt-action barrel manufactured from 416R stainless steel. Chattahoochee Munitions specifies a fast 1:5 twist rate for our CM7S 338 ARC systems.
- 8″ barrel length
- 416R stainless steel
- 5R rifling
- 1:5 twist rate
- Shouldered crown
- 5/8×24 muzzle threads
- Remage barrel-nut mounting system
- E100 Blackout Cerakote
Why Chattahoochee Munitions Uses a 1:5 Twist
The standardized 338 ARC specification uses 1:8 as a practical twist-rate baseline. Chattahoochee Munitions takes a different approach with the CM7S. Based on our experience manufacturing and testing heavy .338-caliber systems, including extensive work with 8.6 Blackout, we specify a 1:5 twist for our bolt-action 338 ARC barrels.
In Chattahoochee Munitions testing, the faster twist has performed particularly well with heavy .338-caliber projectiles such as the Hornady 307-grain Sub-X. That capability is especially relevant to the intended role of an extremely compact firearm such as the 8-inch 338 ARC SBR.
TriggerTech Remington 700 Primary Trigger
The 338 ARC SBR is equipped with a TriggerTech Remington 700 Primary trigger. Flat and curved trigger options are available, with pull weight externally adjustable from approximately 1.5 to 4.0 pounds.
TriggerTech’s Frictionless Release Technology provides a crisp break and short overtravel. Hardened 440C stainless-steel internal components provide corrosion resistance and durability, while CLKR Technology provides defined pull-weight adjustment.
CM7 Billet Chassis – FDE Metallic
The CM7 chassis provides a rigid aluminum foundation for the compact bolt-action system while retaining extensive adjustment and accessory-mounting capability.
- Machined from a single block of billet aluminum
- Flared magazine well for AICS-pattern magazines
- Ambidextrous magazine release
- AR-15 pistol-grip compatibility without an integrated dovetail
- Large trigger guard for gloved operation
- Modular single-bolt stock/brace adapter system
- M-LOK accessory mounting
- Dual integrated QD sling sockets
- Full-length bottom ARCA rail
- FDE Metallic Cerakote
SBR or Pistol Configuration
The 8-inch CM7S can be ordered in two configurations depending on the shooter’s intended application.
SBR configuration: Telescoping buttpad with adjustable cheek riser. Short Barreled Rifle configurations are subject to applicable federal, state, and local requirements and require transfer through an appropriately licensed dealer.
Pistol configuration: Telescoping Tailhook brace with adjustable cheek riser.
CM Precision Vertical Crossover Grip
The chassis is fitted with the CM Precision Vertical Crossover Grip, developed in collaboration with MK Machining. Its near-vertical geometry complements the compact CM7S chassis and provides a natural interface across a variety of shooting positions.
10-Round AICS-Pattern Magazine
Each 338 ARC SBR includes a 10-round MDT polymer 6 ARC AICS-pattern magazine. Chattahoochee Munitions has tested this magazine architecture with 22 ARC, 6 ARC, and 338 ARC in our bolt-action systems.
Why an 8″ 338 ARC?
The primary reason for choosing the 8-inch CM7S is straightforward: compactness.
Based on Chattahoochee Munitions testing of the 338 ARC loads we have evaluated, powder utilization occurs largely around the 12-inch barrel-length range. The 12.5-inch CM7S is therefore the stronger choice when maximizing ballistic efficiency within a short platform is the primary objective.
The 8-inch version makes a deliberate trade. It gives up barrel length to produce a dramatically shorter firearm. Depending on configuration, this CM7S measures as little as approximately 20.5 inches overall.
That distinction gives the 338 ARC SBR a specific role within the CM7S family rather than suggesting that the 8-inch, 12.5-inch, and 16-inch barrels provide identical performance.
Subsonic and Supersonic Capability
The CM7S can use both subsonic and supersonic 338 ARC ammunition. Chattahoochee Munitions places particular emphasis on subsonic-capable firearm systems, making the combination of a manually operated bolt action, compact barrel, and fast 1:5 twist particularly relevant to heavy .338-caliber projectiles.
Because the CM7S is manually operated, ammunition does not need to provide the gas impulse required to cycle a semi-automatic action. This gives the bolt-action platform a fundamentally different operating envelope from a gas-operated AR-15.
CM7S 338 ARC SBR Specifications
- Cartridge: 338 ARC
- Action: Chattahoochee Munitions CM7S
- Action footprint: Remington 700
- Bolt: Three-lug, 60-degree throw
- Bolt face: 6.5 Grendel Type II / .449″
- Barrel: 8″ MÔS-Tek 416R stainless steel
- Rifling: 5R
- Twist: 1:5
- Muzzle thread: 5/8×24
- Barrel finish: E100 Blackout Cerakote
- Trigger: TriggerTech Remington 700 Primary
- Trigger adjustment: 1.5–4.0 lb
- Chassis: CM7 billet aluminum
- Chassis finish: FDE Metallic Cerakote
- Magazine: 10-round MDT polymer 6 ARC AICS-pattern magazine
- Weight: 5 lb 12 oz
- Overall length: 20.5″–28.0″
- Length of pull: 6.0″–13.5″
Explore Containment Zone 338
The 8-inch CM7S represents the compact end of the Chattahoochee Munitions 338 ARC family. Visit Containment Zone 338 to explore CM7S bolt-action firearms, CM15 AR-15 systems, barreled actions, magazines, and technical information about 338 ARC.
338 ARC SBR FAQ
What barrel length does the CM7S 338 ARC SBR use?
This configuration uses an 8-inch MÔS-Tek 416R stainless-steel barrel with 5R rifling and a 1:5 twist.
Why does Chattahoochee Munitions use a 1:5 twist?
CM specifies the faster twist based on our testing and experience with heavy .338-caliber projectiles. In our testing, the 1:5 twist has performed particularly well with heavy projectiles such as the Hornady 307-grain Sub-X.
Why choose the 8-inch CM7S instead of the 12.5-inch version?
The primary advantage is compactness. Based on the loads CM has evaluated, the 12.5-inch configuration provides greater opportunity for powder utilization, while the 8-inch version prioritizes minimum overall length.
Can the 8-inch CM7S be configured as a pistol?
Yes. A pistol configuration with a telescoping Tailhook brace is available. It can also be configured as an SBR with a telescoping buttpad, subject to applicable requirements.
What magazine does the CM7S use?
The firearm includes a 10-round MDT polymer 6 ARC AICS-pattern magazine that Chattahoochee Munitions has tested with 338 ARC in the CM7S platform.
Peter Wilson (verified owner) –