CM15 338 ARC AR SBR – 10″ FDE Metallic
The CM15 338 ARC AR SBR combines the 338 ARC cartridge with a compact semi-automatic AR-15 platform built around a 10.5-inch barrel and fast 1:5 twist. Chattahoochee Munitions integrates billet 7075-T6 receivers, an adjustable gas system, an ODIN Works adjustable buffer, a low-mass bolt carrier group, and a TriggerTech AR15 Duty trigger into a purpose-built short-barreled rifle.
This configuration features FDE Metallic Cerakote on the receivers and 9.5-inch CM15 handguard. The primary SBR configuration uses a six-position adjustable receiver extension and B5 Systems Bravo stock. A pistol configuration with an SBPDW telescoping brace and receiver-extension assembly is also available.
Optics and suppressors shown in product photography are for illustration only and are not included unless specifically identified as part of the selected configuration.
CM15 Billet Upper and Lower Receivers
The 338 ARC AR SBR is built around the CM15 billet receiver set. Both receivers are CNC machined from 7075-T6 aluminum and incorporate ambidextrous controls and a widely flared magazine well.
- AR-15-pattern receiver architecture
- CNC machined from 7075-T6 billet aluminum
- Pictogram-style Fire/Safe markings on both sides
- Lightened fire-control-group faces and magazine well
- Integral trigger guard
- Machined, widely flared magazine well
- Ambidextrous safety
- Ambidextrous magazine release
- Ambidextrous bolt release
- CM15 pivot and takedown pins
- FDE Metallic Cerakote
TriggerTech AR15 Duty Trigger
The CM15 uses the TriggerTech AR15 Duty trigger. Customers can select from three trigger configurations:
- Single-stage straight bow
- Single-stage curved bow
- Two-stage straight bow
These options provide a choice between single-stage and two-stage operation along with straight- and curved-bow configurations.
CM15 Low-Mass Bolt Carrier Group
The CM15 338 ARC AR SBR uses a low-mass bolt carrier group built around a 9310 steel bolt. The bolt incorporates the requisite 6.5 Grendel Type II / .449″ bolt face for the CM15 338 ARC system.
- 9310 steel bolt
- 6.5 Grendel Type II / .449″ bolt face
- High Pressure Tested (HPT) bolt
- Magnetic Particle Inspected (MPI) bolt
- Nitride-coated bolt
- Nitride-coated carrier
- Nitride-coated gas key
- Hardened gas key
- Grade 8 hardened gas-key fasteners
- Staked gas key
- Tool-steel extractor
CM Ambidextrous Charging Handle
The CM15 is equipped with the CM Ambidextrous Charging Handle in collaboration with Breek Arms. Manufactured from 7075 aluminum, the charging handle provides ambidextrous operation from either side of the firearm.
10″ 338 ARC Barrel – 1:5 Twist
The 10.5-inch CM15 uses a 416R stainless-steel barrel with a 1:5 twist. Chattahoochee Munitions uses the faster twist in its short 338 ARC configurations based on our experience with heavy .338-caliber projectiles and compact, subsonic-capable systems.
- 10″ barrel length
- 416R stainless steel
- E100 Blackout Cerakote
- 1:5 twist rate
- Shouldered crown
- 5/8×24 muzzle threads
- .750″ gas journal
- Pistol-length gas system
Adjustable Gas and Buffer System
The 338 ARC AR SBR incorporates adjustment at both the gas system and buffer system. A Superlative Arms .750 adjustable gas block provides gas adjustment at the barrel, while the ODIN Works AR15 Lite Adjustable Buffer provides an additional tuning point at the receiver extension.
This gives the CM15 adjustment at both ends of the operating system rather than relying on a single fixed gas-and-buffer combination.
- Superlative Arms .750 adjustable gas block
- Melonite-treated pistol-length gas tube
- ODIN Works AR15 Lite Adjustable Buffer
- Adjustable buffer weight
CM15 9.5″ M-LOK Handguard
The 10.5-inch CM15 uses a compact 9.5-inch LWS low-profile handguard finished in FDE Metallic Cerakote.
- 6061 aluminum construction
- 9.5″ length
- Dual-taper attachment system
- Steel barrel nut
- QD sling attachment points at 3 and 9 o’clock
- M-LOK mounting surfaces on sides and bottom
- Full-length Picatinny top rail
- FDE Metallic Cerakote
338 ARC AR SBR Configuration
The primary configuration of this 338 ARC AR SBR uses a six-position adjustable receiver extension with a B5 Systems Bravo stock. Combined with the 10.5-inch barrel and 9.5-inch handguard, the SBR provides a substantially shorter package than the 16-inch CM15 while retaining a conventional rifle stock.
A pistol configuration is also available with an SBPDW telescoping brace and receiver-extension assembly. The FDE Metallic configuration carries the Cerakote finish onto the corresponding receiver-extension components.
Short-barreled-rifle configurations are subject to applicable federal, state, and local requirements and transfer through an appropriately licensed dealer.
338 ARC Muzzle Device Options
The barrel uses 5/8×24 muzzle threads for compatible .338-caliber muzzle devices. Available configurations may include mounting solutions from Q, Dead Air, SilencerCo, Rugged, and other compatible systems. Contact Chattahoochee Munitions regarding specific muzzle-device selections or applicable price differences.
10-Round 338 ARC AR-15 Magazine
The CM15 includes a 10-round DURAMAG SS AR-15-pattern magazine vetted by Chattahoochee Munitions for 338 ARC. The magazine uses 410 stainless-steel construction and is selected as part of the complete CM15 system. For optimal feeding and reliable operation, Chattahoochee Munitions recommends loading the magazine with no more than eight rounds.
Additional magazines are available through the CM 338 ARC AR15 Magazine product page.
Why a 10″ 338 ARC AR SBR?
The 10.5-inch configuration takes advantage of one of the defining characteristics of 338 ARC: the ability to place a .338-caliber cartridge within the AR-15 platform envelope while maintaining a compact overall package.
In Chattahoochee Munitions testing of the 338 ARC loads we have evaluated, powder utilization occurs largely around the 12-inch barrel-length range. The 10.5-inch 338 ARC AR SBR deliberately trades some barrel length for a shorter overall platform rather than simply pursuing maximum velocity.
The 1:5 twist also reflects CM’s experience with heavy .338-caliber projectiles. In Chattahoochee Munitions testing, the Hornady 307-grain Sub-X has performed better from our 1:5 twist systems than from the standardized 1:8 twist configuration. This is a CM testing observation rather than a claim that 1:5 is universally preferable for every 338 ARC load.
Compact 338 ARC in the AR-15 Platform
The CM15 combines the compact AR-15 platform envelope with a dedicated 338 ARC operating system. The requisite 6.5 Grendel Type II / .449″ bolt face, CM-vetted magazine, adjustable gas block, adjustable buffer, and dedicated barrel are integrated into the complete firearm rather than treating 338 ARC as simply a barrel conversion.
For customers seeking a compact semi-automatic 338 ARC system, the CM15 provides an alternative to the manually operated CM7S bolt-action family.
Compare CM15 and CM7S configurations through Containment Zone 338.
CM15 338 ARC AR SBR Specifications
- Cartridge: 338 ARC
- Platform: CM15 / AR-15 pattern
- Operating system: Gas-operated semi-automatic
- Primary configuration: Short-barreled rifle
- Upper/lower: 7075-T6 billet aluminum
- Finish: FDE Metallic Cerakote
- Barrel: 10″ 416R stainless steel
- Barrel finish: E100 Blackout Cerakote
- Twist: 1:5
- Muzzle thread: 5/8×24
- Gas journal: .750″
- Gas system: Pistol length
- Gas block: Superlative Arms .750 adjustable
- Buffer: ODIN Works AR15 Lite Adjustable Buffer
- Bolt: 9310 steel, HPT/MPI
- Bolt face: 6.5 Grendel Type II / .449″
- BCG: CM15 low-mass, nitride
- Charging handle: CM Ambidextrous Charging Handle in collaboration with Breek Arms
- Trigger: TriggerTech AR15 Duty
- Trigger options: Single-stage straight bow, single-stage curved bow, or two-stage straight bow
- Handguard: CM15 LWS 9.5″ M-LOK
- SBR configuration: Six-position adjustable receiver extension with B5 Systems Bravo stock
- Optional pistol configuration: SBPDW telescoping brace and receiver-extension assembly
- Magazine: 10-round DURAMAG SS, CM vetted for 338 ARC. For optimal feeding and reliable operation, Chattahoochee Munitions recommends loading the magazine with no more than eight rounds.
- Weight: 6 lb 4 oz with unloaded magazine and no accessories
- Overall length: 26.5375″–29.0375″
- Length of pull: 10.25″–12.750″
Explore Containment Zone 338
Visit Containment Zone 338 to compare CM15 semi-automatic systems, CM7S bolt-action configurations, barreled actions, magazines, and technical information about 338 ARC.
338 ARC AR SBR FAQ
What is the CM15 338 ARC AR SBR?
The CM15 is Chattahoochee Munitions’ compact gas-operated AR-15-pattern platform chambered in 338 ARC. This SBR configuration uses a 10.5-inch 1:5 twist barrel and a B5 Systems Bravo stock.
Why does the 10.5-inch CM15 use a 1:5 twist?
Chattahoochee Munitions uses a faster 1:5 twist in its short 338 ARC configurations. In CM testing, the Hornady 307-grain Sub-X has performed better from our 1:5 systems than from the standardized 1:8 configuration.
Is a pistol configuration also available?
Yes. Customers who prefer a pistol configuration can select an SBPDW telescoping brace and receiver-extension assembly instead of the SBR stock configuration.
Does the CM15 have adjustable gas and buffer systems?
Yes. The CM15 combines a Superlative Arms .750 adjustable gas block with an ODIN Works AR15 Lite Adjustable Buffer.
What bolt face does the CM15 use?
The CM15 uses a 9310 steel bolt incorporating the requisite 6.5 Grendel Type II / .449″ bolt face. The bolt is High Pressure Tested and Magnetic Particle Inspected.
What trigger does the CM15 use?
The CM15 uses a TriggerTech AR15 Duty trigger with single-stage straight, single-stage curved, and two-stage straight configurations available.
What charging handle does the CM15 use?
The firearm uses the CM Ambidextrous Charging Handle in collaboration with Breek Arms, manufactured from 7075 aluminum.
What magazine is included?
The CM15 includes a 10-round DURAMAG SS AR-15-pattern magazine vetted by Chattahoochee Munitions for 338 ARC. For optimal feeding and reliable operation, Chattahoochee Munitions recommends loading the magazine with no more than eight rounds.
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