CM15-SD 300 Blackout 5″ 1:5 AR15 SBR or Pistol – Color Selectable

300 Blackout PDW – CM15 5″ SD Pistol or SBR

The CM15 300 Blackout PDW is an ultra-compact SD-style semi-automatic firearm manufactured by Chattahoochee Munitions around a 5-inch, 1:5 twist barrel. Its micro-length gas system and extended suppressor-compatible handguard create the smallest tucked-suppressor configuration in the CM15 300 Blackout family.

When a compatible suppressor is installed, part of the suppressor extends beneath the handguard. This maintains useful forward gripping and accessory space while controlling the overall length of the suppressed firearm.

The CM15 is available as either a pistol or an SBR. Chattahoochee Munitions prefers the stocked SBR configuration when legally practical because the shoulder stock provides greater stability, control and consistency. The pistol remains available for customers whose intended use or ownership requirements favor that classification.

The suppressor, optic and other pictured accessories are not included unless specifically selected or stated in the product options.

Ultra-Compact 300 Blackout PDW

The 300 Blackout PDW is designed for customers who deliberately prioritize minimum overall length, maneuverability and suppressed subsonic operation. Its five-inch barrel is not intended to duplicate the ballistic performance of CM’s preferred 10- to 10.5-inch general-purpose barrel range.

The five-inch barrel and SD handguard instead create a specialized personal-defense-weapon configuration for:

• Compact suppressed subsonic shooting
• Close-range training and range use
• Confined-space handling
• Vehicle transport where legally permitted
• Customers who prefer an SD-style profile
• Applications where suppressed overall length matters

SD Suppressor-Under-Handguard Configuration

SD originated from the German word Schalldämpfer, meaning sound suppressor or silencer. In modern firearm terminology, SD commonly describes a firearm where part of the suppressor extends beneath the handguard or forend.

The 300 Blackout PDW uses an 8.25-inch overall-length handguard over a five-inch barrel. This positions the forward portion of the handguard beyond the barrel shoulder and creates space for a compatible suppressor beneath the handguard.

This architecture may also be described as a tucked suppressor, shrouded suppressor or suppressor under the handguard. It is not an integrally suppressed firearm. The suppressor remains a separate, removable NFA-regulated component.

Selectable Cerakote Finish

The five-inch CM15 SD is offered as one configurable product rather than separate pages based only on color. Customers may choose from:

• Cobalt Kinetics Green: Cobalt Kinetics Green receivers and handguard with Coyote furniture
• FDE Metallic: FDE Metallic receivers and handguard with Coyote furniture
• Black Tungsten: Black Tungsten receivers and handguard with Black furniture

Finish selection does not alter the barrel, gas system, operating components or performance of the firearm.

CM15 Billet Receiver Set

• Mil-spec interface dimensions for AR-15 components
• CNC-machined 7075-T6 billet aluminum construction
• Selectable Cerakote finish
• 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
• Ultra-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 catch and release
• B5 Systems grip matched to the selected furniture color

TriggerTech Duty Trigger Options

Each 300 Blackout PDW is offered with a TriggerTech AR-15 Duty trigger. Customers can select from three 3.5-pound configurations:

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

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

Pistol or SBR Configuration

Pistol: SBPDW brace and compatible receiver-extension assembly finished to match the selected Cerakote configuration.

SBR: Six-position receiver extension with a B5 Systems Bravo stock matched to the selected furniture color.

CM prefers the SBR when legally practical because its stock provides more consistent support and control. An SBR must be transferred through an appropriately licensed FFL/SOT following the applicable federal process.

A suppressor is also an NFA-regulated item unless otherwise exempted by applicable law. Customers remain responsible for compliance with federal, state and local requirements for both the firearm and suppressor.

Both configurations use an ODIN Works adjustable AR-15 buffer. Buffer adjustment complements the adjustable gas block and permits final refinement without relying on unnecessarily heavy reciprocating mass.

CM15 Bolt Carrier Group

• 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.

Micro-Length Adjustable Gas System

The 300 Blackout PDW uses a micro-length gas system because the five-inch barrel is too short to accommodate conventional pistol-length gas. This is a dimensional requirement specific to the five-inch configuration.

• Melonite-treated micro-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 semi-automatic 300 Blackout firearm. Subsonic ammunition, supersonic ammunition and suppressors can create substantially different operating conditions.

With an enclosed suppressor, pressure returns through both the gas tube and chamber. The gas block addresses the root cause by controlling how much gas enters the operating system. Buffer adjustment provides final refinement after the gas setting is established.

The objective is reliable cycling with the lightest practical buffer and the minimum amount of gas required to operate the firearm.

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

Explore the 300 Blackout gas-system and tuning guide for detailed information about gas adjustment, buffer adjustment, ejection patterns and single-round testing.

Five-Inch 1:5 Twist Barrel

• 5-inch barrel length
• 4140 GBQ steel
• Nitride finish
• 1:5 twist rate
• Shouldered crown
• 5/8×24 muzzle threads
• .750-inch gas-block journal
• Micro-length gas system

The fast 1:5 twist is essential to the purpose of the five-inch barrel. It provides the rotational stability needed for long, heavy subsonic bullets despite the extremely limited barrel length.

A five-inch barrel does not provide the powder utilization or velocity available from CM’s preferred 10- to 10.5-inch configuration. The defining advantage of the 300 Blackout PDW is its reduced length, particularly when combined with a compact suppressor.

SLR Rifleworks SD ZRO Handguard

The SLR Rifleworks SD ZRO handguard has a 4.25-inch base length and an 8.25-inch overall length. Its enlarged suppressor channel allows part of a dimensionally compatible suppressor to extend beneath the forward portion of the handguard.

• 4.25-inch base length
• 8.25-inch overall length
• 1.8-inch internal diameter
• Free-floating construction
• Continuous Picatinny top rail
• M-LOK accessory-mounting surfaces
• Limited-rotation QD sling sockets
• Suitable for compatible direct-thread suppressor configurations
• Cerakote matched to the selected firearm finish

Suppressor Compatibility and Heat

The nominal 1.8-inch handguard ID does not mean every suppressor smaller than 1.8 inches is automatically compatible. Clearance must account for actual suppressor diameter, dimensional tolerances, accessory fasteners, muzzle-device geometry and the chosen mounting system.

Direct-thread suppressors generally simplify the tucked configuration by eliminating bulky mounting components. Other mounting systems may work when their outside diameter and installation requirements provide adequate clearance.

Any suppressor used with this firearm must be rated by its manufacturer for 300 Blackout and a five-inch barrel. A suppressor’s caliber rating alone does not establish short-barrel compatibility.

A tucked or shrouded suppressor transfers heat into the surrounding handguard. Customers should use appropriate handling practices and understand that the handguard can become hot during sustained firing.

Enclosed Suppressor Preferred for Subsonic Use

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 supplied by an enclosed suppressor. A flow-oriented suppressor can 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 incoming gas to be reduced rather than masking excessive gas with a heavier buffer alone.

Suppressor choice, ammunition and gas settings function as an interconnected system. Even switching between different subsonic loads can affect cycling and ejection behavior.

Subsonic and Supersonic Ammunition

The 300 Blackout PDW can use both subsonic and supersonic ammunition, but its primary 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 the five-inch barrel limits its velocity potential. Supersonic ammunition also creates a ballistic crack that a suppressor cannot eliminate.

Black Butterfly Ammunition is an appropriate source for purpose-designed 300 Blackout ammunition.

Explore the 300 Blackout subsonic guide for additional information about barrel length, twist rate, ammunition and suppression.

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 magazines are available through the CM15 300 Blackout magazine page.

Product Specifications

• Manufacturer: Chattahoochee Munitions
• Model: CM15 300 Blackout PDW
• Caliber: 300 AAC Blackout / 300 BLK
• Classification: Pistol or SBR
• Barrel: 5-inch 4140 GBQ steel, nitrided
• Twist rate: 1:5
• Gas system: Micro length
• Gas block: Superlative Arms .750-inch adjustable
• Buffer: ODIN Works adjustable AR-15 buffer
• Muzzle thread: 5/8×24
• Handguard: SLR Rifleworks SD ZRO, 4.25-inch base and 8.25-inch overall length
• Handguard ID: 1.8 inches
• Trigger: TriggerTech Duty with selectable 3.5-pound configuration
• Magazine: One CM-vetted ETS 30-round magazine
• Finish: Selectable Cobalt Kinetics Green, FDE Metallic or Black Tungsten
• Overall length: 24.625 to 27.125 inches without suppressor
• Weight: 5 pounds 14 ounces with an unloaded magazine, without suppressor or accessories
• Length of pull: 10.25 to 12.75 inches

Note: The suppressor adds length and weight according to the suppressor and mounting system selected. 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 Sector 300

This 300 Blackout PDW occupies the shortest SD position within the CM15 family. Customers wanting the muzzle and suppressor completely forward of the handguard should consider the conventional five-inch CM15. Customers seeking greater powder utilization should consider a 7.5- or 10.5-inch CM15.

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

Frequently Asked Questions

What is a 300 Blackout PDW?

A 300 Blackout PDW is a compact personal-defense-weapon-style firearm chambered in 300 Blackout. This CM15 uses a five-inch barrel, micro-length gas system and extended suppressor-compatible handguard.

Is the suppressor included?

No. A suppressor is not included unless specifically stated in the selected product options.

Is this integrally suppressed?

No. The suppressor remains a separate, removable component. The SD designation refers to a compatible suppressor extending beneath the handguard.

What suppressor fits beneath the handguard?

Compatibility depends on the suppressor’s outside diameter, mounting system, barrel-length rating and required clearance. The handguard has a nominal 1.8-inch internal diameter, but every proposed combination must be verified before use.

Why does the five-inch barrel use micro-length gas?

The barrel is too short to accommodate conventional pistol-length gas. The micro-length system positions the gas port where sufficient operating pressure remains available to cycle the firearm.

Why does the barrel use a 1:5 twist?

The fast 1:5 twist provides the rotational stability needed for long, heavy subsonic bullets fired through the extremely short five-inch barrel.

Is this available as a pistol or an SBR?

Yes. Customers can select a pistol with an SBPDW brace or an SBR with a six-position receiver extension and B5 Systems Bravo stock. CM prefers the SBR when legally practical because its stock provides greater stability and control.

Can it use subsonic and supersonic ammunition?

Yes. Different loads and suppressors can change cycling and ejection behavior, so the adjustable gas block may require retuning when the operating configuration changes.

Will the handguard become hot?

Yes. A suppressor beneath the handguard transfers heat into the surrounding handguard. Appropriate handling precautions should be used, particularly during sustained firing.

Is every CM15 test fired?

Yes. Every CM 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?

One CM-vetted ETS 30-round magazine is included. Chattahoochee Munitions evaluates magazine compatibility as part of the complete firearm system.

What are the firearm’s dimensions and weight?

Without a suppressor installed, the firearm measures 24.625 to 27.125 inches overall and weighs 5 pounds 14 ounces with an unloaded magazine and no accessories. The selected suppressor and mounting system add their own length and weight.