300 Blackout AR15 Pistol or SBR – CM15 10.5″
The Chattahoochee Munitions CM15 is a complete 300 Blackout AR15 pistol manufactured around the barrel length, twist rate and adjustable operating system CM prefers for subsonic and suppressed 300 Blackout use. This FDE Metallic configuration is available as either a pistol or short-barreled rifle, allowing the customer to select the classification and rear assembly that fit the intended application.
The 10.5-inch barrel falls within CM’s optimal 10 to 10.5-inch range for 300 Blackout. Its 1:5 twist provides the rotational stability preferred for long, heavy subsonic bullets. A pistol-length gas system, Superlative Arms adjustable gas block and ODIN Works adjustable buffer allow the operating system to be refined for the ammunition and suppressor being used.
Every CM semi-automatic firearm is test-fired and verified for proper operation before shipment. Chattahoochee Munitions addresses barrel gas-port sizing, gas-block alignment and baseline operating-system adjustment during manufacturing.
Explore the complete Sector 300 ecosystem for additional CM15 and CM7S firearms, technical resources, magazines and supporting products.
Why Choose a 10.5″ 300 Blackout AR15 Pistol?
The 300 Blackout AR15 pistol combines CM’s preferred barrel length with compact handling and a pistol-appropriate rear configuration. It is a practical choice for customers who want a short 300 Blackout firearm without selecting the SBR option.
Most useful powder consumption occurs within approximately 9 to 10.5 inches. Extending the barrel beyond that range does not provide a meaningful advantage for CM’s preferred subsonic use. The 10.5-inch barrel preserves the cartridge’s efficiency while leaving sufficient room for a conventional pistol-length gas system.
Customers who prefer the consistent shoulder contact of a conventional adjustable stock may select the SBR configuration. CM considers the SBR the preferred overall form of the system, but both classifications use the same barrel, upper receiver, gas system and handguard.
10.5-Inch 1:5-Twist Barrel
The barrel is manufactured from 4150 CMV steel and receives a nitride treatment. Its 1:5 twist is particularly important when stabilizing long, heavy subsonic bullets at relatively low velocity.
- Caliber: 300 AAC Blackout / 300 BLK
- Barrel length: 10.5 inches
- Barrel material: 4150 CMV steel
- Barrel finish: Nitrided
- Twist rate: 1:5
- Crown: Shouldered crown
- Muzzle thread: 5/8×24
- Gas journal: .750 inch
- Gas-system length: Pistol length
Pistol-Length Gas and Adjustable Operation
This 300 Blackout AR15 pistol uses a pistol-length gas system because the cartridge must retain sufficient operating pressure when firing subsonic ammunition. Moving the gas port farther forward would reduce the pressure available to operate the action and could make reliable subsonic cycling more difficult.
The Superlative Arms .750-inch adjustable gas block regulates the gas entering the operating system. The ODIN Works adjustable buffer provides a secondary tuning control after the appropriate gas setting has been established.
The objective is reliable feeding, extraction, ejection and last-round bolt lock with the lightest practical buffer and the minimum gas required. Adding buffer mass before correcting excessive gas treats a symptom instead of addressing the source of the operating pressure.
Read the 300 Blackout gas-system guide for CM’s complete explanation of gas adjustment, ejection patterns, buffer tuning and suppressor backpressure.
Subsonic and Suppressed Performance
A 10.5-inch 300 Blackout AR15 pistol is particularly well suited to heavy subsonic ammunition and an enclosed suppressor. An enclosed suppressor generates backpressure that helps operate the action when subsonic ammunition produces comparatively limited gas pressure.
Flow-through suppressors reduce backpressure and are generally better suited to supersonic-focused cartridges. Reduced backpressure can work against reliable subsonic cycling. Conversely, supersonic ammunition combined with an enclosed suppressor may generate enough backpressure that the adjustable gas block must be closed substantially.
Changing ammunition can alter cycling even when both loads are subsonic. The gas setting should therefore be established using the ammunition, magazine and suppressor that will normally be used with the firearm.
For additional information about barrel length, twist rate and ammunition selection, read the 300 Blackout subsonic guide. Purpose-specific loads are also available from Black Butterfly Ammunition.
SLR Rifleworks ZRO 9.5″ M-LOK Handguard
The CM15 uses an SLR Rifleworks ZRO 9.5-inch M-LOK handguard. Its exact 9.5-inch length leaves the muzzle of the 10.5-inch barrel accessible for compatible 5/8×24 muzzle devices and suppressor-mounting systems.
The free-floating handguard includes a continuous Picatinny top rail, M-LOK accessory mounting and two limited-rotation QD sling sockets. Its forward accessory space is well suited to appropriately mounted lights, night-vision equipment and infrared aiming devices.
- 9.5-inch exact length
- 1.35-inch internal diameter
- Free-floating design
- Mil-spec hardcoat-anodized construction
- Hardcoat-anodized 7075 aluminum barrel nut
- No barrel-nut timing or shims required
- Slip-fit locking mounting system
- Two limited-rotation QD sling sockets
- Continuous Picatinny top rail
- M-LOK accessory attachment
- FDE Metallic Cerakote exterior finish
CM15 Billet Receiver Set
The upper and lower receivers of this 300 Blackout AR15 pistol are CNC-machined from 7075-T6 billet aluminum. Their close fit contributes to the rigid, substantial feel associated with the CM15 platform.
- Mil-spec component interface dimensions
- CNC-machined 7075-T6 billet aluminum construction
- Ambidextrous pictogram-style Safe and Fire markings
- Lightened fire-control-group faces and magazine well
- Integral trigger guard for additional receiver strength
- Machined rather than broached magazine well
- Wide magazine-well flare
- Lower receiver weight of approximately 8 ounces
- FDE Metallic Cerakote finish
Ambidextrous Controls and TriggerTech Duty Trigger
The CM15 lower receiver includes ambidextrous controls and a customer-selectable TriggerTech AR15 Duty trigger. Available options are single-stage curved, single-stage straight and two-stage straight. All three options have a 3.5-pound total pull weight.
- CM ambidextrous safety selector
- CM ambidextrous magazine release
- CM15 ambidextrous bolt release
- CM15 pivot and takedown pins
- TriggerTech AR15 Duty trigger selected by the customer
- B5 Systems Coyote grip
Pistol and SBR Configurations
Pistol Configuration
The primary 300 Blackout AR15 pistol configuration uses the same CM15 upper, barrel, handguard and adjustable operating system as the SBR while providing a pistol-appropriate rear assembly.
- SBPDW brace and receiver-extension assembly
- FDE Metallic Cerakote on applicable extension components
- ODIN Works adjustable AR-15 buffer
CM-Preferred SBR Configuration
The available SBR option replaces the pistol rear assembly with a conventional adjustable receiver extension and stock. The stock provides consistent shoulder contact while retaining the compact handling of the 10.5-inch barrel.
- Six-position adjustable receiver extension
- B5 Systems Bravo stock
- ODIN Works adjustable AR-15 buffer
- Transfer through an appropriate FFL/SOT under applicable NFA requirements
The selected configuration determines the firearm’s classification. Customers are responsible for compliance with all applicable federal, state and local requirements.
CM15 Low-Mass Bolt Carrier Group
The CM15 low-mass bolt carrier group works with the adjustable gas block and adjustable buffer as part of the firearm’s complete operating system. Regulating the gas first allows the carrier and buffer to operate without unnecessary speed or reciprocating mass.
- 9310 steel bolt
- High-pressure-tested bolt
- Magnetic-particle-inspected bolt
- Nitride-coated bolt
- Nitride-coated carrier
- Nitride-coated gas key
- Gas key hardened to USGI specifications
- Grade 8 hardened gas-key fasteners
- Gas key staked to military specifications
- Tool-steel extractor
Upper Receiver Components
- CM15 ambidextrous charging handle machined from 7075 aluminum
- CM15 dust cover
- Melonite-treated pistol-length gas tube
- Superlative Arms .750-inch adjustable gas block with Melonite finish
Selectable 5/8×24 Muzzle Device
The barrel is threaded 5/8×24 and can be configured with an appropriate muzzle device or suppressor-mounting interface selected from the available product options. The final device should match the suppressor or unsuppressed configuration the customer intends to use. Certain selections may affect the final price.
Legacy photography may show a muzzle device that is not the current default configuration. The completed firearm is not restricted to the device pictured.
CM-Vetted ETS Magazine
This 300 Blackout AR15 pistol includes one CM-vetted ETS 30-round magazine. Chattahoochee Munitions treats magazine selection as part of the firearm’s operating system because cartridge presentation and feeding can vary with different 300 Blackout bullet profiles.
Additional magazines are available through the 300 Blackout magazine product page.
Factory-Tested and Verified
Every 300 Blackout AR15 pistol or SBR manufactured by Chattahoochee Munitions is test-fired and checked for proper semi-automatic operation before shipment. Gas-port sizing, gas-block alignment and baseline tuning are addressed during manufacturing instead of being left as unresolved customer troubleshooting.
The factory setting establishes a reliable operational baseline. Final gas adjustment may still be appropriate when the customer changes ammunition or adds a suppressor with a substantially different backpressure profile.
Complete Specifications
- Manufacturer: Chattahoochee Munitions
- Model: CM15
- Caliber: 300 AAC Blackout / 300 BLK
- Available classifications: Pistol or SBR
- Barrel: 10.5-inch 4150 CMV, nitrided
- Twist rate: 1:5
- Gas system: Pistol length
- Gas block: Superlative Arms .750-inch adjustable
- Buffer: ODIN Works adjustable AR-15 buffer
- Muzzle thread: 5/8×24
- Trigger: TriggerTech AR15 Duty, 3.5-pound total pull
- Handguard: SLR Rifleworks ZRO 9.5-inch M-LOK
- Magazine: One CM-vetted ETS 30-round magazine
- Finish: FDE Metallic Cerakote with Coyote furniture
- Pistol overall length: 26.5375–29.0375 inches
- Pistol length of pull: 10.25–12.75 inches
- Listed weight: 6 pounds, 10 ounces with an unloaded magazine and no accessories
Note: The listed overall length and length of pull apply to the pistol configuration represented by the available technical baseline. The SBR configuration varies with stock position. Weight and dimensions shown elsewhere in the product interface may represent packaged shipping measurements.
Optics and suppressors shown in product photography are for illustration only unless expressly included in the selected product options.
Limited Lifetime Warranty
- Limited to the original purchaser
- Limited regarding functional performance
- Limited regarding the firearm’s original configuration
Frequently Asked Questions
Why is 10.5 inches an effective 300 Blackout barrel length?
Chattahoochee Munitions considers approximately 10 to 10.5 inches optimal for its preferred subsonic use of 300 Blackout. It provides effective powder utilization without adding unnecessary barrel length.
Why does this barrel use a 1:5 twist?
The faster 1:5 twist provides additional rotational stability for long, heavy subsonic bullets traveling at relatively low velocity.
Can this firearm be ordered as an SBR?
Yes. Customers may select the CM-preferred SBR configuration with a six-position receiver extension and B5 Systems Bravo stock. The SBR is subject to applicable transfer and registration requirements.
Can the pistol use a suppressor?
Yes. The barrel has 5/8×24 muzzle threads and remains accessible beyond the 9.5-inch handguard. An enclosed suppressor is generally preferable when reliable subsonic operation and maximum sound reduction are the primary objectives.
Will changing ammunition affect the gas setting?
It can. Different subsonic and supersonic loads may produce different operating pressure. The adjustable gas block and adjustable buffer allow the system to be refined for the ammunition and suppressor being used.
A Complete 10.5″ CM15 System
The FDE Metallic CM15 300 Blackout AR15 pistol combines CM’s preferred 10.5-inch barrel length, a 1:5 twist, pistol-length gas, adjustable gas control, an adjustable buffer and a free-floating ZRO handguard. The complete firearm is manufactured, test-fired and verified by Chattahoochee Munitions for compact handling and suppressed subsonic performance.
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