CM15 300 Blackout 16″ AR15 Rifle – FDE Metallic

300 Blackout AR15 Rifle – CM15 16″ FDE Metallic

The Chattahoochee Munitions CM15 is a complete 300 Blackout AR15 rifle manufactured for shooters who want the cartridge’s suppressor compatibility and subsonic capability in a conventional 16-inch rifle configuration. The 16-inch barrel avoids short-barreled-rifle classification while retaining the adjustable operating system required to manage the broad range of ammunition and suppressor combinations encountered with 300 Blackout.

This CM15 is manufactured around matched billet receivers, a pistol-length gas system, a Superlative Arms adjustable gas block and an ODIN Works adjustable buffer. Chattahoochee Munitions uses these controls to regulate the gas entering the action before relying on additional buffer mass to counter excessive carrier speed. Every CM semi-automatic firearm is test-fired and verified for proper operation before shipment.

Explore the complete Sector 300 ecosystem for additional 300 Blackout firearms, technical information, magazines and supporting products.

A Conventional 16-Inch 300 Blackout Configuration

This 300 Blackout AR15 rifle uses a 16-inch CrMV barrel with a black nitride finish and 1:7 twist. Chattahoochee Munitions considers approximately 10 to 10.5 inches and a 1:5 twist optimal for its preferred subsonic use of 300 Blackout. The purpose of this 16-inch configuration is different: it gives customers a complete rifle that does not require the additional federal requirements associated with an SBR.

For customers seeking a conventionally classified 300 Blackout AR15 rifle, the 16-inch barrel provides a straightforward alternative to a pistol or registered short-barreled rifle. It also accommodates a full-length handguard and familiar rifle handling without changing the cartridge’s fundamental gas-system requirements.

The longer barrel should not be interpreted as necessary for complete powder utilization or as automatically superior for suppressed subsonic ammunition. Most useful powder consumption occurs within approximately 9 to 10.5 inches. The 16-inch barrel instead serves shooters who prioritize rifle classification, a full-length handguard and conventional handling.

• Caliber: 300 AAC Blackout / 300 BLK
• Barrel length: 16 inches
• Barrel material: CrMV steel
• Barrel finish: Black nitride
• Twist rate: 1:7
• Crown: Shouldered crown
• Muzzle thread: 5/8×24
• Gas journal: .750 inch
• Gas-system length: Pistol length

Pistol-Length Gas for Reliable 300 Blackout Operation

A 16-inch 300 Blackout barrel should not be assigned a longer gas system simply because the barrel is longer. The cartridge produces its pressure differently from conventional supersonic-focused AR-15 cartridges. CM uses a pistol-length gas system on this rifle to provide the operating pressure needed for subsonic ammunition, particularly when the firearm is suppressed.

The 300 Blackout gas-system guide explains how ammunition, suppressor design, gas adjustment and buffer settings interact. Even two subsonic loads can produce meaningfully different cycling behavior.

A properly regulated 300 Blackout AR15 rifle should receive only the gas required to feed, extract, eject and lock the bolt open after the final round. Sending additional gas into the action increases carrier speed, felt recoil, component stress and gas exposure without improving useful performance.

The Superlative Arms adjustable gas block allows the operating system to be regulated at the source. The correct approach is to send only enough gas into the system to achieve reliable feeding, extraction, ejection and last-round bolt lock. Buffer adjustment provides a secondary control after the gas setting has been established.

Suppressor Use and Ammunition Selection

A properly configured 300 Blackout AR15 rifle should accommodate both subsonic and supersonic ammunition, but changing loads or adding a suppressor may require adjustment. An enclosed suppressor is generally preferable when the primary objective is reliable subsonic operation. Its backpressure helps operate the action when ammunition produces relatively limited gas pressure.

A flow-through suppressor can be useful with supersonic-focused cartridges, but reduced backpressure can work against reliable subsonic 300 Blackout cycling. Conversely, supersonic ammunition fired through an enclosed suppressor may produce substantial backpressure. In that situation, the adjustable gas block may need to be closed considerably to prevent excessive carrier speed and gas entering the receiver.

For more information about load selection, barrel length and twist rate, read the 300 Blackout subsonic guide. Ammunition from Black Butterfly Ammunition is also a legitimate option for shooters evaluating purpose-specific 300 Blackout loads.

CM15 Billet Receiver Set

The upper and lower receivers of this 300 Blackout AR15 rifle are CNC-machined from 7075-T6 billet aluminum and finished in FDE Metallic Cerakote. Their close fit contributes to the solid 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 Lower Controls and TriggerTech Duty Trigger

The CM15 lower receiver includes ambidextrous controls and a customer-selectable TriggerTech AR15 Duty trigger. Available trigger options are single-stage curved, single-stage straight and two-stage straight. Each option has a 3.5-pound total pull weight.

• CM ambidextrous safety selector
• CM ambidextrous magazine release
• CM15 pivot and takedown pins
• CM15 ambidextrous bolt release
• TriggerTech AR15 Duty trigger selected by the customer
• B5 Systems Coyote grip

Receiver Extension Assembly

• B5 Systems SOPMOD stock in Coyote
• CM mil-spec-diameter buffer tube with FDE Metallic Cerakote
• QD receiver endplate
• ODIN Works adjustable AR-15 buffer

CM15 Low-Mass Bolt Carrier Group

The CM15 low-mass bolt carrier group works with the adjustable gas block and adjustable buffer to create a tunable operating system. The objective is reliable operation with the lightest practical buffer and the minimum gas required, rather than using unnecessary buffer mass to mask an overgassed firearm.

• 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

15-Inch CM15 Handguard

The 15-inch CM15 LWS low-profile handguard provides support for a conventional rifle-length shooting position while protecting the gas system. Its FDE Metallic Cerakote matches the receiver set and buffer tube.

• 6061 aluminum construction
• Dual-taper attachment system
• Steel barrel nut
• Integrated QD attachment points at the 3 and 9 o’clock positions
• M-LOK attachment surfaces on the sides and bottom
• Continuous Picatinny top rail
• B5 Systems Coyote rail covers

5/8×24 Muzzle-Device Options

The barrel is threaded 5/8×24 and can be configured with an appropriate muzzle device selected from the available product options. This allows the customer to match the 300 Blackout AR15 rifle to a compatible suppressor-mounting system or unsuppressed muzzle device. Some selections may change the final price.

Because suppressor mounting standards and customer requirements differ, the final muzzle device should be selected according to the suppressor that will actually be used. Chattahoochee Munitions does not limit this rifle to the device shown in legacy product photography.

CM-Vetted ETS Magazine

This rifle includes one CM-vetted ETS 30-round magazine. Magazine selection is treated as part of the operating system rather than as an incidental accessory. Proper cartridge presentation and feeding are especially important when moving between different 300 Blackout bullet profiles.

Additional magazines are available through the 300 Blackout magazine product page.

Factory Testing and Operational Verification

Every 300 Blackout AR15 rifle manufactured by Chattahoochee Munitions is test-fired and checked for proper semi-automatic operation before shipment. CM addresses gas-block alignment, barrel gas-port sizing and baseline system adjustment during manufacturing. This process establishes a functional starting point for the complete rifle rather than leaving basic gas-system correction to the customer.

Final settings can still change when the owner introduces different ammunition or a suppressor with a substantially different backpressure profile. The adjustable gas block and adjustable buffer make those changes manageable without replacing core operating components.

Complete Specifications

• Manufacturer: Chattahoochee Munitions
• Model: CM15
• Caliber: 300 AAC Blackout / 300 BLK
• Firearm type: Semi-automatic rifle
• Barrel: 16-inch CrMV, black nitride
• Twist rate: 1:7
• 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: CM15 LWS 15-inch M-LOK
• Magazine: One CM-vetted ETS 30-round magazine
• Finish: FDE Metallic Cerakote with Coyote furniture
• Overall length: 33.25–36.50 inches
• Length of pull: 11.25–14.50 inches
• Weight: 6 pounds, 11 ounces with unloaded magazine and no accessories

Note: Weight and dimensions shown elsewhere in the product interface may represent packaged shipping measurements.

Limited Lifetime Warranty

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

Frequently Asked Questions

Why does a 16-inch 300 Blackout rifle use pistol-length gas?

Pistol-length gas provides the pressure needed to operate reliably with subsonic 300 Blackout ammunition. Barrel length alone does not justify moving the gas port farther forward. The adjustable gas block then regulates the amount of gas entering the action.

Can this rifle use both subsonic and supersonic ammunition?

Yes. The firearm can use both, but different loads may require gas adjustment. Switching between two subsonic loads can also change cycling because ammunition does not produce identical pressure and dwell characteristics.

Is this 300 Blackout AR15 rifle suppressor ready?

Yes. The barrel has 5/8×24 muzzle threads and selectable muzzle-device options. An enclosed suppressor is normally the more appropriate choice when reliable subsonic operation is the primary goal.

Why choose the 16-inch configuration?

The principal advantage is obtaining a conventionally classified rifle without the federal registration requirements associated with an SBR. The 16-inch barrel also supports a full-length handguard and conventional rifle handling.

Does Chattahoochee Munitions test the completed rifle?

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

A Complete and Tunable 300 Blackout Rifle

The CM15 16-inch FDE Metallic 300 Blackout AR15 rifle combines conventional rifle classification with a properly configured pistol-length gas system, adjustable gas control and an adjustable buffer. Its billet receiver set, TriggerTech Duty trigger, CM-vetted ETS magazine and verified factory operation make it a complete CM firearm—not a collection of loosely matched components.