CM15-SD 300 Blackout 7.5″ 1:5 AR15 SBR or Pistol – Color Selectable

300 Blackout Tucked Suppressor SD Pistol or SBR

The CM15 300 Blackout Tucked Suppressor is an SD-style semi-automatic firearm manufactured by Chattahoochee Munitions around a 7.5-inch, 1:5 twist barrel and extended suppressor-compatible handguard. When a compatible suppressor is installed, part of the suppressor extends beneath the handguard to create a compact, integrated profile without permanently attaching the suppressor to the firearm.

This CM15 is available as either an SBR or a pistol. 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 7.5-inch barrel prioritizes minimum overall length over the greater powder utilization available from the 10- to 10.5-inch barrel range. Its fast 1:5 twist provides the rotational stability needed for long, heavy subsonic bullets fired through the shorter barrel.

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

What Makes This an SD Configuration?

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

The 300 Blackout Tucked Suppressor configuration uses a 10.7-inch overall-length handguard over a 7.5-inch barrel. The additional handguard length creates four inches of coverage beyond the barrel shoulder, allowing a compatible suppressor to extend beneath the forward portion of the handguard.

This is not an integrally suppressed firearm. The suppressor remains a separate, removable NFA-regulated component. The SD designation describes the suppressor-under-handguard architecture.

Tucked or Shrouded Suppressor Configuration

A tucked suppressor is also sometimes described as a shrouded suppressor or a suppressor under the handguard. These terms describe the same basic architecture: part of the removable suppressor extends beneath an enlarged handguard while enough of the suppressor remains exposed for practical handling and removal.

Chattahoochee Munitions uses 300 Blackout Tucked Suppressor as the primary description because it clearly distinguishes this SD system from an integrally suppressed firearm. The suppressor remains a separate component and is not included unless specifically selected or stated in the product options.

Compact Suppressed Architecture

The principal advantage of the 300 Blackout Tucked Suppressor system is its ability to combine a very short barrel with useful forward handguard length. The shooter gains additional gripping and accessory-mounting area without leaving the entire suppressor exposed beyond a short conventional handguard.

• Compact suppressed subsonic shooting
• Close-range training and range use
• Confined-space handling
• SD-style suppressor-under-handguard profile
• Night-vision and infrared accessory configurations
• Applications where suppressor-equipped overall length matters

Selectable Cerakote Finish

The CM15 7.5-inch 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
• 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 grip matched to the selected color configuration

TriggerTech Duty Trigger Options

Each 300 Blackout Tucked Suppressor firearm 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

Additional manufacturer information is available directly from TriggerTech.

SBR or Pistol Configuration

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

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

CM prefers the SBR configuration when legally practical because its shoulder 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.

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, carrier and 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, dust cover and forward assist.

Adjustable Pistol-Length Gas System

The 300 Blackout Tucked Suppressor uses a pistol-length gas system. The 7.5-inch barrel provides sufficient room for pistol gas, while CM’s shorter 5-inch firearms require a micro-length gas system.

• 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 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 can then provide final refinement. 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 tuning are addressed during manufacturing.

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

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 provides greater rotational stability for long, heavy subsonic bullets than the former 1:7 configuration. This is particularly important when a short barrel is paired with subsonic ammunition and a suppressor.

A 7.5-inch barrel does not provide the same powder utilization as CM’s preferred 10- to 10.5-inch general-purpose configuration. The advantage is a more compact suppressed firearm.

SLR Rifleworks SD 6.7-Inch Handguard

The 300 Blackout Tucked Suppressor uses an SLR Rifleworks SD handguard with a 6.7-inch base length and 10.7-inch overall length. Its enlarged internal diameter creates clearance for compatible suppressors beneath the forward section.

• 6.7-inch base length
• 10.7-inch overall length
• Four inches from the barrel shoulder to the end of the handguard
• 1.8-inch internal diameter
• Compatible with suppressors up to 1.75 inches in outside diameter
• Four special forward accessory nuts
• Forward accessories accommodate suppressors up to 1.7 inches in outside diameter
• Minimum recommended suppressor length of 4.5 inches
• 6061-T6 aluminum construction
• Free-floating design
• Mil-spec hardcoat-anodized finish beneath the selected 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
• Handguard weight of approximately 11.4 ounces with barrel nut and hardware

300 Blackout Tucked Suppressor Compatibility

Suppressor diameter must be verified before installation. The handguard supports compatible suppressors up to 1.75 inches in outside diameter, but accessory fasteners installed around the covered portion can reduce available clearance.

The four included forward accessory nuts support compatible accessories without extending excessively into the suppressor channel. These accommodate suppressors up to 1.7 inches in outside diameter when positioned correctly.

A suppressor at least 4.5 inches long is recommended so sufficient suppressor body extends beyond the handguard. Actual exposed length depends on the muzzle device, mounting system and suppressor selected.

A 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. Compatibility must account for suppressor diameter, mounting access, heat and removal for inspection and maintenance.

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 provided 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 pressure with a heavier buffer alone.

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

Subsonic and Supersonic Ammunition

The 300 Blackout Tucked Suppressor can use both subsonic and supersonic 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 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 Tucked Suppressor SD
• Caliber: 300 AAC Blackout / 300 BLK
• Classification: SBR or pistol
• Barrel: 7.5-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
• Handguard: SLR Rifleworks SD, 6.7-inch base and 10.7-inch overall length
• Handguard ID: 1.8 inches
• Maximum suppressor OD: Up to 1.75 inches, subject to mounting and accessory clearance
• Recommended minimum suppressor length: 4.5 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: 27 to 29.5 inches without suppressor
• Weight: 6 pounds 5 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 Tucked Suppressor configuration occupies the compact SD position within the CM15 family. Customers wanting the suppressor completely forward of the handguard should consider a conventional 7.5-inch CM15. Customers seeking greater powder utilization should consider the 10.5-inch CM15 or 10.5-inch SD.

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 tucked suppressor configuration?

A 300 Blackout Tucked Suppressor configuration positions part of a compatible suppressor beneath an enlarged handguard. The suppressor remains removable and is not permanently integrated into the firearm.

What is a shrouded suppressor?

A shrouded suppressor is partially surrounded by the firearm’s handguard or forend. In this application, shrouded and tucked suppressor describe the same general suppressor-under-handguard architecture.

Is the suppressor included?

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

What suppressor diameter fits beneath the handguard?

The handguard accommodates compatible suppressors up to 1.75 inches in outside diameter. When accessories are mounted over the suppressor area, the forward accessory hardware supports suppressors up to 1.7 inches in outside diameter.

How long should the suppressor be?

A suppressor at least 4.5 inches long is recommended. Actual exposed length depends on the suppressor, muzzle device and mounting system selected.

Is this integrally suppressed?

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

Is this available as a pistol or an SBR?

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

Why does the barrel use a 1:5 twist?

The 1:5 twist provides greater rotational stability for long, heavy subsonic bullets fired through the 7.5-inch barrel.

Does it use pistol-length gas?

Yes. The 7.5-inch barrel uses a pistol-length gas system. Only CM’s shorter 5-inch 300 Blackout configurations require micro-length gas.

Can it fire subsonic and supersonic ammunition?

Yes. Changing ammunition or suppressors can alter system pressure and cycling, so the adjustable gas block may require retuning.

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 are the firearm’s dimensions and weight?

Without a suppressor installed, the firearm measures 27 to 29.5 inches overall and weighs 6 pounds 5 ounces with an unloaded magazine and no accessories. The selected suppressor and mounting system add their own length and weight.