CM7S 338 ARC 12.5″ Bolt Action Short Barrel Rifle WOOX Walnut Stock 338ARC .338ARC

338 ARC Rifle: 12.5″ Bolt Action Short Barrel Rifle – SBR – Black Tungsten

The modern tactical landscape is continuously searching for the ultimate balance between hard-hitting, large-bore energy and compact maneuverability. Enter the 338 ARC rifle (Advanced Rifle Cartridge). Purpose-built to deliver devastating close-to-medium range terminal ballistics out of a standard AR-15 platform, this round changes the math on short-barrel performance. It successfully bridges the gap between traditional intermediate cartridges and heavy subsonic options, establishing itself as an absolute powerhouse for pig hunting, home defense, and specialized tactical operations.

At Chattahoochee Munitions, we took this cutting-edge cartridge and engineered a tight-tolerance, premium rifle system specifically optimized for it. The 338 ARC rifle is built from the ground up to handle high gas volume, minimize recoil, and ensure flawless cycling, whether you are running massive subsonic projectiles or high-velocity supersonic hunting loads. Hand-finished in our stunning Black Tungsten Cerakote, this 338 ARC rifle delivers heavy-hitting energy in an incredibly fast-handling package.

Technical Specifications & Factory Description (338 ARC Rifle)

From the Workshop: This is a 12.5″ 338 ARC rifle from Chattahoochee Munitions. This will be one of the sturdiest-feeling weapons, as everything is designed in tight tolerances. All of our rifles are equipped with HIPERFIRE (High Performance Firearms) Triggers; all are 2.5lb single-stage Reflex (curved) or Competition (straight with shoe); Competition is pictured. Odin Adjustable Buffers and Superlative Arms Adjustable Gas Blocks are standard on our rifles.

Complete Component Breakdown

• CM15 Upper and Lower Receiver:

  • Mil-spec dimensions to mate with standard AR15 components

  • CNC machined from 7075-T6 billet aluminum blocks

  • ‘Pictogram’ style Fire/Safe markings on both sides

  • Light-Weight FCG Faces and lightened Mag-well

  • Integral trigger guard for added lower receiver structural strength

  • Machined (not broached) Mag-well with wide flare for fast reloads

  • Lightweight Lower Receiver Weight = 8.0 oz

  • Black Tungsten Cerakote finish

• Lower Parts & Furniture:

  • CM Ambi Safety Selector & CM Ambi Mag Release

  • CM15 Pivot and Takedown Pins

  • HIPERFIRE 2.5lb single-stage Reflex (curved), Competition (straight with shoe), or X2S Mod3 (two-stage straight) Trigger

  • CM15 Ambi Bolt Catch & Release

  • B5 Systems Black Tactical Grip

  • B5 Systems Bravo Stock – Black

  • CM Milspec Buffer Tube – Black Tungsten Cerakote

  • QD Endplate & Odin Adjustable Buffer AR15

• Upper Receiver Assembly & Gas System:

  • CM15 Low Mass Bolt Carrier Group: 9310 steel HPT Bolt (High Pressure Tested/Proof), MPI Bolt (Magnetic Particle Inspected), Nitride-coated bolt, Nitride-coated Carrier, Nitride-coated Gas Key, Gas Key Hardened to USGI Specifications, Grade 8 Hardened Fasteners, Key Staked Per Mil-Spec, Tool Steel Extractor, and specialized Lightening Cuts to reduce reciprocating mass.

  • CM15 Ambi Charging Handle – 7075 Aluminum

  • CM15 Dust Cover and Forward Assist

  • CM Carbine Length Gas Tube – Melonite

  • Superlative Arms .750 Adjustable Gas Block – Melonite

  • CM15 LWS 11″ M-LOK Handguard: Black Tungsten Cerakote, 6061 Aluminum, Dual Taper Attachment System, Steel Barrel Nut, QD Attachment points at 3 and 9 o’clock positions, M-LOK slots on the sides and bottom, Full Picatinny Top Rail.

  • B5 Systems Black Rail Covers

• Barrel & Ballistic Specifications:

  • CM15 338 ARC 12.5″ Precision Barrel

  • 416R Stainless Steel base with Black Cerakote finish

  • Fast Twist Rate optimized for stabilizing heavy, large-diameter .338 bullets

  • Shouldered crown with 5/8×24 thread pitch (standard for large-bore applications)

  • .750 gas journal with an optimized Carbine Length Gas System

• Dimensions & Included Extras:

  • Magazine: 1x 10-round High-Reliability ARC DuraMag

  • Overall Weight (OAW): 6 lbs, 4 oz (with unloaded magazine, no accessories)

  • Warranty: Limited Lifetime Warranty (to the original purchaser, covering functional performance and original manufacturing specifications)

The Power of the 338 ARC Rifle

The 338 ARC rifle family introduces an entirely new level of ballistic performance to the compact AR-15 footprint. While the AR-15 has historically been limited to small or intermediate bore diameters, the 338 ARC rifle uses a modified, high-volume case design to push heavy, large-diameter .338 caliber projectiles.

The primary advantage of a 338 ARC rifle is its incredible flexibility. It is designed to fire heavy subsonic rounds (ranging from 200 to 250+ grains) quietly and efficiently out of a short barrel, generating massive kinetic energy transmission upon impact. At the same time, it can push lighter supersonic projectiles to impressive velocities, making it an incredibly effective short-range hunting rifle that completely outperforms traditional options like 300 Blackout or 7.62x39mm in pure cross-sectional delivery.

Premium Engineering: The Chattahoochee Munitions Difference

Building a flawless, large-bore 338 ARC rifle requires extreme attention to detail. Large projectiles generate complex pressure curves and increased physical forces inside a small-frame rifle. At Chattahoochee Munitions, we tune every rifle system to absolute perfection.

1. Billet Aluminum Receivers with Strict Tolerances

Every CM15 receiver set is CNC-machined from 7075-T6 billet aluminum. By moving away from common cast or forged receivers, we can maintain microscopic tolerances where the upper and lower halves mate together. This completely eliminates loose wiggle, reducing mechanical play and improving shot-to-shot consistency. The receiver set is wrapped in a hard-wearing Black Tungsten Cerakote coat to protect against harsh field environments.

2. High-Grade 416R Stainless Steel Barrel

The 12.5″ precision barrel is machined from premium 416R stainless steel—a material trusted globally for match-grade precision. The twist rate is carefully chosen to properly stabilize heavy, long-for-caliber .338 bullets at both supersonic and subsonic speeds. With a standard 5/8×24 thread pitch, it provides a perfectly square shoulder for mounting muzzle devices or suppressors.

3. Advanced Gas Control and Recoil Mitigation

Managing a short-barreled, large-bore platform requires exact control over the gas impulse. The CM15 comes equipped with a Superlative Arms Adjustable Gas Block alongside our proprietary CM15 Low Mass Bolt Carrier Group.

By utilizing the patented bleed-off technology of the Superlative Arms block, excess high-pressure gas is vented safely out the front rather than forced back into the receiver. When paired with our lightweight carrier and the Odin Adjustable Buffer, the reciprocating mass drops dramatically. This keeps your muzzle completely flat, reduces felt recoil to a soft push, and keeps your sight picture perfectly aligned for rapid follow-up shots.

+--------------------------------------------------------+
|             CM15 GAS & RECOIL SYSTEM SCHEMATIC         |
+--------------------------------------------------------+
| Superlative Arms Bleed-Off Gas Block (Vents Excess Pressure) |
|                         ↓                              |
| CM15 Low Mass Bolt Carrier (Reduces Reciprocating Weight)  |
|                         ↓                              |
| Odin Adjustable Buffer Assembly (Fine-Tunes Cycling Speed) |
+--------------------------------------------------------+
| EFFECT: Soft Felt Recoil, Minimal Carbon Influx, Flawless Cycling |
+--------------------------------------------------------+

4. Precision Trigger Selection

A high-performance rifle demands an elite trigger. We outfit our builds with crisp 2.5 lb single-stage or two-stage HIPERFIRE triggers. These triggers offer a remarkably clean break with an exceptionally short, positive reset. Whether you prefer the traditional feel of a curved Reflex shoe or the linear mechanical leverage of a straight Competition trigger, your interface with this rifle will feel exceptionally tactile.

Custom Muzzle Device Configurations

Since short-barrel rifles are highly effective when paired with a silencer, the CM15 338 ARC rifle features a robust 5/8×24 muzzle thread configuration. You can select your preferred muzzle device directly from our factory dropdown menu:

• Thread Protector Only: A clean, minimal option for running a clean barrel.

• Dead Air Keymo Brake / Flash Hider: A quick-detach interface designed specifically for Dead Air suppressor compatibility.

• SilencerCo ASR Brake: A rugged, industry-proven multi-lug quick-detach mount.

• Rugged 3-Port Brake: Drastically cuts down lingering muzzle blast while accommodating Rugged suppressors.

• Yankee Hill Brake: A durable, positive-locking mount for YHM systems.

Frequently Asked Questions (FAQ)

What makes the 338 ARC rifle different from the 300 Blackout?

While both cartridges excel in short-barrel and subsonic applications, the 338 ARC uses a significantly larger bullet diameter (.338″ vs. 308″) and a larger case capacity based on the ARC/Grendel family. This allows a 338 ARC rifle to throw heavier projectiles with greater cross-sectional area, resulting in deeper penetration and massive energy transfer compared to standard 300 Blackout loads.

Can I run standard 5.56 NATO or .223 magazines in this rifle?

No. The 338 ARC rifle case features a wider body diameter than standard 5.56 ammo. To ensure completely reliable feeding and proper cartridge stacking, you must use ARC-specific magazines. This rifle includes a premium 10-round DuraMag built specifically to handle this cartridge geometry.

Is the 12.5″ barrel long enough to get full burnout of the powder?

Yes. The 338 ARC rifle is highly efficient and designed specifically to maximize powder burn within shorter barrels. A 12.5″ barrel offers an excellent balance, giving you full velocity potential for supersonic hunting rounds while keeping the overall footprint incredibly short and agile when using a suppressor.

How do I properly adjust the gas block for subsonic vs. supersonic ammunition?

The included Superlative Arms gas block uses an adjustment screw that vents excess pressure out of the front. We recommend setting the gas block up to reliably lock back the bolt on an empty magazine using your softest subsonic load. Once set, supersonic rounds will cycle flawlessly with zero over-gassing issues.

Where can I find other uppers or standalone parts for my build?

If you want to swap configurations on your lower receiver or explore different lengths, check out our CM15 Uppers Category to view all available upper assemblies. For long-range bolt-action builds, look into our precision CM7S Bolt Action line.

Purchase Information & ATF Compliance

Chattahoochee Munitions is a fully licensed Type 07 FFL Manufacturer and Class 2 SOT based out of Roswell, Georgia.

Please note that because this configuration features a 12.5″ barrel paired with a rifle stock, it is classified as a Short Barreled Rifle (SBR) under the National Firearms Act (NFA). This item requires an ATF Form 4 transfer to your local dealer and the purchase of an NFA tax stamp. To learn more about ordering firearms online, please read our comprehensive Official Firearms Buying Guide.

Custom-built queues and tuning verification take approximately two weeks before freight shipment. Experience large-bore AR-15 performance like never before with the Chattahoochee Munitions CM15.