CM15 300 Blackout 7.5″ AR15 SBR or Pistol – Cobalt Kinetics Green

300 Blackout CQB Pistol or SBR – CM15 7.5″

The CM15 300 Blackout CQB is a compact AR-15 firearm manufactured by Chattahoochee Munitions for close-quarters handling, suppressed subsonic shooting and applications where overall length matters. Its 7.5-inch barrel creates a highly maneuverable configuration while retaining the adjustable gas and buffer system necessary to manage the broad operating range of 300 Blackout ammunition.

This firearm is available as either a pistol or an SBR. We prefer the stocked SBR configuration when legally practical because the shoulder stock provides greater stability, control and consistency. The pistol configuration remains available for customers whose intended use or ownership requirements favor that classification.

The 7.5-inch barrel is intentionally more compact than the 10- to 10.5-inch length we consider optimal for general-purpose 300 Blackout performance. That tradeoff makes the 300 Blackout CQB particularly useful where maneuverability and suppressor-equipped overall length take priority. A 1:5 twist rate provides the rotational stability needed for heavy subsonic bullets from this shortened barrel.

Compact Close-Quarters Configuration

CQB is commonly used to describe firearms configured for close-quarters environments. For this CM15, the term reflects its physical characteristics: short overall dimensions, fast handling and a barrel-and-handguard combination designed to remain practical after a suppressor is installed.

The conventional 6.7-inch handguard ends behind the muzzle, leaving the muzzle device and suppressor mounting interface readily accessible. This differs from an SD configuration, where part of the suppressor extends beneath the handguard.

The 300 Blackout CQB is particularly well suited to:

• Compact suppressed shooting
• Close-range training and range use
• Confined-space handling
• Property and home-defense applications
• Vehicle transport where legally permitted
• Shooters prioritizing minimum firearm length

CM15 Upper and Lower Receiver Set

The matched CM15 receiver set is manufactured from 7075-T6 billet aluminum. Tight receiver fit, ambidextrous controls and a flared machined magazine well establish a solid foundation for the complete firearm.

• Mil-spec interface dimensions for AR-15 components
• CNC-machined 7075-T6 billet aluminum construction
• Cobalt Kinetics Green Cerakote
• Ambidextrous pictogram-style Safe and Fire markings
• Lightened fire-control-group faces and magazine well
• Integral trigger guard for additional strength
• Machined, rather than broached, magazine well
• Wide magazine-well flare
• Lower receiver weight of approximately 8 ounces

Ambidextrous Lower Controls

• CM ambidextrous safety selector
• CM ambidextrous magazine release
• CM15 pivot and takedown pins
• CM15 ambidextrous bolt release
• B5 Systems Coyote grip

TriggerTech Duty Trigger Options

Each 300 Blackout CQB firearm is offered with a 3.5-pound TriggerTech Duty trigger. Customers can select the trigger geometry and operating style that best suit their intended application:

• Single-stage curved
• Single-stage straight
• Two-stage straight with a 3.5-pound total pull weight

TriggerTech’s design provides a clean and predictable break while maintaining the durability appropriate for a working AR-15. Additional manufacturer information is available from TriggerTech.

Pistol or SBR Configuration

Pistol: SBPDW brace and compatible receiver-extension assembly finished in Cobalt Kinetics Green Cerakote.

SBR: Six-position receiver extension with a B5 Systems Bravo stock.

The SBR is the preferred configuration when its additional stock support and adjustability match the customer’s intended use. An SBR is regulated under the National Firearms Act and must be transferred through an appropriately licensed FFL/SOT following the required federal process. Customers remain responsible for compliance with federal, state and local law.

Both configurations use an ODIN Works adjustable AR-15 buffer. Buffer adjustment complements the adjustable gas block, allowing the firearm to be tuned without relying on unnecessarily heavy reciprocating mass.

CM15 Low-Mass Bolt Carrier Group

• Low-mass carrier configuration
• 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

The upper assembly also includes a CM15 ambidextrous charging handle machined from 7075 aluminum and a CM15 dust cover.

Adjustable Pistol-Length Gas System

The 300 Blackout CQB uses a pistol-length gas system. Pistol gas is necessary for dependable 300 Blackout operation across the cartridge’s wide pressure range, including heavy subsonic ammunition. The 7.5-inch barrel provides adequate space for a conventional pistol-length system; the shorter micro-length gas system is reserved for CM’s 5-inch configurations.

• Melonite-treated pistol-length gas tube
• Superlative Arms .750-inch adjustable gas block
• ODIN Works adjustable buffer
• Gas system configured and verified during manufacturing

An adjustable gas block is a requisite component on a properly configured 300 Blackout semi-automatic firearm. Subsonic and supersonic loads can produce substantially different operating pressure, and adding an enclosed suppressor introduces additional backpressure through the chamber.

The gas block addresses the root cause by controlling how much gas enters the operating system. Buffer adjustment can then be used for final refinement when necessary. The objective is reliable operation with the lightest practical buffer and no more gas than the firearm needs.

Every CM semi-automatic firearm is test fired and its operation verified before shipment. Gas-port sizing, gas-block alignment and baseline system tuning are addressed during manufacturing rather than being left for the customer to diagnose.

For a detailed explanation of gas adjustment, ejection patterns and single-round testing, explore the 300 Blackout gas-system and tuning guide.

7.5-Inch 1:5 Twist Barrel

• 7.5-inch barrel length
• 4150 chrome-moly-vanadium steel
• Nitride finish
• 1:5 twist rate
• Shouldered crown
• 5/8×24 muzzle threads
• .750-inch gas-block journal
• Pistol-length gas system

The fast 1:5 twist is especially important in this short barrel. It provides greater rotational stability for long, heavy subsonic bullets than the former 1:7 configuration. This makes the revised barrel substantially better aligned with the suppressed, subsonic purpose of the 300 Blackout cartridge.

A 7.5-inch barrel does not provide the same powder utilization as CM’s preferred 10- to 10.5-inch configuration. Its advantage is compactness. This 300 Blackout CQB firearm is intended for customers who knowingly prioritize minimum length over the broader ballistic efficiency of a 10.5-inch barrel.

SLR Rifleworks ZRO 6.7-Inch Handguard

The conventional configuration uses an SLR Rifleworks ZRO 6.7-inch M-LOK handguard. Its short length provides clearance for the muzzle device and suppressor attachment interface while preserving useful mounting space.

• 6.7-inch exact length
• 1.35-inch internal diameter
• Free-floating construction
• Mil-spec hardcoat-anodized finish beneath the Cerakote
• Hardcoat-anodized 7075 aluminum barrel nut
• No barrel-nut timing or shims required
• Slip-fit locking attachment system
• Two limited-rotation QD sling sockets
• Continuous Picatinny top rail
• M-LOK accessory mounting surfaces
• Useful forward mounting space for compatible night-vision and infrared equipment
• Cobalt Kinetics Green Cerakote

Suppressor and Muzzle-Device Options

The 5/8×24 muzzle threads accept commonly used 300 Blackout muzzle devices and suppressor-mounting systems. Available options may include direct-thread devices, flash hiders, brakes and suppressor mounts. Pricing can vary by the device selected.

For subsonic 300 Blackout, an enclosed suppressor is generally preferable to a low-backpressure or flow-through design. Subsonic ammunition often benefits from the additional backpressure an enclosed suppressor supplies. A flow-oriented suppressor can work against that requirement and may reduce the operating energy available to cycle the firearm.

Supersonic ammunition used with an enclosed suppressor can generate considerably more backpressure. The adjustable gas block allows gas flow to be reduced for that configuration instead of attempting to mask excessive gas with a heavier buffer alone.

Suppressor choice, ammunition and gas settings operate as a system. Changing any one of them can require a tuning adjustment. Even different subsonic loads may not produce identical cycling behavior.

Subsonic and Supersonic Ammunition

The 300 Blackout CQB can use both subsonic and supersonic 300 Blackout ammunition, but its principal purpose is compact suppressed operation with subsonic loads.

Subsonic ammunition provides the cartridge’s defining suppressed capability. Supersonic ammunition produces greater velocity and energy, but it also changes gas-system behavior and creates a ballistic crack that a suppressor cannot eliminate.

Load selection should be based on the intended application, bullet construction and the firearm’s verified operating configuration. Black Butterfly Ammunition is an appropriate source for purpose-designed 300 Blackout ammunition.

For more information about twist rate, barrel length and ammunition selection, explore the 300 Blackout subsonic guide.

CM-Vetted 300 Blackout Magazine

Each firearm includes one CM-vetted ETS 30-round magazine. Magazine performance is evaluated as part of the complete firearm system rather than assuming every nominally compatible AR-15 magazine will feed every 300 Blackout load equally well.

Additional vetted magazines are available in the CM15 300 Blackout magazine listing.

Product Specifications

• Manufacturer: Chattahoochee Munitions
• Model: CM15
• Caliber: 300 AAC Blackout / 300 BLK
• Classification: Pistol or SBR
• Barrel length: 7.5 inches
• Barrel material: 4150 CMV
• Barrel finish: Nitride
• 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
• Handguard: SLR Rifleworks ZRO 6.7-inch M-LOK
• Trigger: TriggerTech Duty with selectable 3.5-pound configuration
• Magazine: One CM-vetted ETS 30-round magazine
• Finish: Cobalt Kinetics Green with Coyote furniture
• Overall length: 23.875 to 26.375 inches
• Weight: 6 pounds with an unloaded magazine and no accessories
• Length of pull: 10.25 to 12.75 inches

Note: Weight and dimensions shown on another product tab are for shipping purposes.

Limited Lifetime Warranty

• Limited to the original purchaser
• Limited regarding functional performance
• Limited regarding the firearm’s original configuration

Explore the Complete 300 Blackout Ecosystem

The CM15 7.5-inch firearm occupies the compact CQB position within Chattahoochee Munitions’ 300 Blackout lineup. Customers wanting greater powder utilization and a more general-purpose configuration should consider a 10.5-inch CM15. Customers wanting a suppressor recessed beneath the handguard should consider the dedicated 7.5-inch SD configuration.

Explore Sector 300 to compare CM15 semi-automatic firearms, CM7S bolt actions, uppers, barreled actions, magazines and supporting 300 Blackout resources.

Frequently Asked Questions

What is a 300 Blackout CQB firearm?

A 300 Blackout CQB firearm is a compact 300 Blackout configuration intended for maneuverability in close quarters and confined spaces. This CM15 uses a 7.5-inch barrel and 6.7-inch handguard to minimize overall length while retaining an adjustable gas system, adjustable buffer and suppressor-ready muzzle threads.

Is this CM15 available as a pistol or an SBR?

Yes. Customers may select either a pistol configuration with an SBPDW brace or an SBR configuration with a six-position receiver extension and B5 Systems Bravo stock. Chattahoochee Munitions prefers the SBR when legally practical because the shoulder stock provides greater stability and control. The SBR requires the applicable federal transfer process through an appropriately licensed FFL/SOT.

Why does this 7.5-inch barrel use a 1:5 twist?

The 1:5 twist provides greater rotational stability for long, heavy subsonic bullets fired through the shortened 7.5-inch barrel. This makes it better suited to the suppressed, subsonic purpose of the cartridge than the former 1:7 configuration.

Is a 7.5-inch barrel optimal for 300 Blackout?

The 7.5-inch barrel is optimized for compactness rather than maximum powder utilization. Chattahoochee Munitions considers 10 to 10.5 inches the optimal general-purpose barrel range for 300 Blackout. The shorter barrel is intended for customers who prioritize minimum overall length and close-quarters handling.

Does the 7.5-inch CM15 use pistol-length gas?

Yes. This firearm uses a pistol-length gas system. The 7.5-inch barrel has sufficient room for pistol gas, while CM’s shorter 5-inch 300 Blackout configurations require a micro-length gas system.

Can this 300 Blackout CQB firearm use a suppressor?

Yes. The barrel has 5/8×24 muzzle threads, and the conventional 6.7-inch handguard leaves the muzzle device and suppressor interface accessible. The firearm can be ordered with an appropriate muzzle device or suppressor-mounting system.

Is the suppressor recessed beneath the handguard?

No. This is the conventional 7.5-inch configuration, with the suppressor mounted beyond the end of the handguard. Customers wanting a suppressor recessed beneath the handguard should consider the dedicated 7.5-inch SD configuration.

Why does the firearm have an adjustable gas block and adjustable buffer?

Subsonic ammunition, supersonic ammunition and suppressors can produce substantially different operating conditions. The Superlative Arms adjustable gas block controls the amount of gas entering the operating system, while the ODIN Works adjustable buffer supports final refinement. Gas adjustment should address the root cause before buffer weight is changed.

Can it fire both subsonic and supersonic ammunition?

Yes. The 300 Blackout CQB can fire both subsonic and supersonic 300 Blackout ammunition. Different loads can change cycling and ejection behavior, however, so the gas system may require adjustment when changing ammunition or suppressor configurations.

Is every CM15 test fired?

Yes. Every Chattahoochee Munitions semi-automatic firearm is test fired and checked for proper operation. Gas-port sizing, gas-block alignment and baseline tuning are addressed during manufacturing.

What magazine is included?

The firearm includes one CM-vetted ETS 30-round magazine. Chattahoochee Munitions evaluates magazine performance as part of the complete firearm system rather than assuming every nominally compatible AR-15 magazine will feed every 300 Blackout load equally well.

What is the overall length and weight?

The overall length is 23.875 to 26.375 inches, depending on adjustment. The firearm weighs 6 pounds with an unloaded magazine and no accessories. Measurements shown elsewhere in the product interface may represent packaged shipping dimensions rather than the firearm itself.