WARNING: This CM10 configuration is designed exclusively for compatible subsonic 308 Winchester ammunition. Firing supersonic ammunition through the CM10 SUBSONIC is not supported and can be dangerous. The firearm requires an enclosed suppressor for reliable semi-automatic cycling. Do not fire it without confirming that the ammunition, suppressor and firearm configuration are compatible.
CM10 308 Subsonic AR10 SD SBR
The CM10 308 Subsonic AR10 is a specialized semi-automatic firearm developed around heavy subsonic 308 Winchester ammunition, a 12.5-inch 1:5 twist barrel and the additional backpressure supplied by an enclosed suppressor.
CM recommends the SBR configuration, which uses a B5 Systems Bravo stock and carbine receiver extension with adjustment notches. A pistol configuration with a brace is also available for customers who prefer that classification.
This is not a conventional short-barreled AR10. Its barrel twist, gas system, adjustable buffer and suppressor-enclosing SD handguard operate as one system. The 1:5 twist stabilizes subsonic projectiles weighing 220 grains and heavier, while the adjustable operating system allows the firearm to cycle multiple compatible subsonic loads with an enclosed suppressor attached.
The CM10 uses a conventional dual-feed LR/SR magazine system. One 20-round Magpul PMAG 7.62 magazine is included where permitted by law.
Explore CM’s complete family of 308 Winchester firearms, ammunition, magazines and technical guides in District 308.
SBR and Pistol Options
- SBR configuration: B5 Systems Bravo stock with a carbine receiver extension and multiple adjustment notches
- Pistol configuration: Adjustable pistol brace in place of the shoulder stock
The SBR configuration is an NFA firearm and must complete the applicable federal transfer process. The customer selects a local FFL/SOT during checkout, and CM coordinates the required dealer documentation on the back end.
Review CM’s NFA firearms information for transfer guidance and available Form 4 services.
Color-Selectable CM10 Configuration
This product is color selectable. Choose the available CM finish through the product options when ordering. Product photographs may show a specific finish, optic or suppressor for illustration, but the selected options determine the delivered firearm.
The billet upper receiver, lower receiver, handguard and selected receiver-extension components are finished according to the chosen configuration. Small controls, the bolt carrier group and other functional components retain their specified protective finishes.
Dedicated Subsonic Operating System
A standard 308 semi-automatic rifle is configured around the pressure and dwell time produced by supersonic ammunition. A subsonic load produces substantially less gas pressure and normally will not cycle a conventional AR10.
The CM10 SUBSONIC uses a dedicated operating configuration with an adjustable gas block, adjustable AR10 buffer and low-mass bolt carrier group. An enclosed suppressor retains additional gas long enough to help operate the action. That suppressor backpressure is part of the system rather than an unwanted side effect.
The adjustable operating system allows the firearm to cycle multiple compatible subsonic loads rather than limiting it to one projectile. Bullet weight alone does not determine cycling. Projectile design, powder selection, pressure curve, suppressor design and gas and buffer settings can all affect operation.
CM has verified the firearm with its 300-grain Maker REX ammunition. Other compatible subsonic loads using projectiles of 220 grains and heavier can also stabilize and cycle, although changes in ammunition or suppressor may require gas or buffer adjustment.
A flow-through or low-back-pressure suppressor may release gas too efficiently to cycle this firearm reliably. CM therefore requires an appropriately rated enclosed suppressor for semi-automatic operation.
The 308 Suppressor Guide explains why CM recommends different suppressor designs for supersonic semi-automatics, subsonic semi-automatics and bolt actions.
12.5-Inch 1:5 Twist Subsonic Barrel
The 12.5-inch barrel is machined from 416R stainless steel and finished in E100 Blackout Cerakote. Its 1:5 twist is selected to stabilize subsonic projectiles weighing 220 grains and heavier, including the 300-grain Maker REX.
The 300-grain Maker REX measures 2.06 inches long and is among the heaviest commercially available .308 projectiles. CM’s load averages approximately 1,005 feet per second from this barrel. The combination of projectile length and subsonic velocity requires substantially more rotational speed than a conventional 1:8 or 1:10 twist barrel can provide.
The 1:5 twist is not limited to the 300-grain projectile. It provides the fast rotation needed to stabilize a range of heavy subsonic bullets beginning at approximately 220 grains.
The shouldered crown protects the muzzle. The barrel uses 5/8×24 threads for direct attachment of a compatible suppressor. This product does not include a muzzle-device selection or a quick-detach suppressor mount.
Barrel Specifications
- Chambering: 308 Winchester
- Barrel length: 12.5 inches
- Material: 416R stainless steel
- Finish: E100 Blackout Cerakote
- Twist rate: 1:5
- Recommended subsonic projectile weight: 220 grains and heavier
- Crown: Shouldered
- Suppressor attachment: Direct thread
- Muzzle threads: 5/8×24
- Gas journal: .750 inch
SD Suppressor-Enclosing Handguard
The CM10 SD uses a free-floating SLR SD ZRO handguard measuring 11.3 inches to the muzzle and 15.3 inches in overall length. The extended handguard partially encloses a compatible direct-thread suppressor, producing the integrated profile associated with CM’s SD configurations.
The handguard has a 1.8-inch internal diameter. Suppressor outside diameter and installation clearance must be confirmed before use. Not every 308 suppressor will fit inside the handguard.
SD Handguard Features
- Length to muzzle: 11.3 inches
- Overall length: 15.3 inches
- Internal diameter: 1.8 inches
- Handguard material: 6061 aluminum
- Barrel nut material: 7075 aluminum
- Free-floating design
- Full-length Picatinny top rail
- M-LOK mounting on the sides and bottom
- QD sling attachments at the 3 and 9 o’clock positions
A suppressor is not included. Select an enclosed, 5/8×24 direct-thread suppressor rated for 308 Winchester, the 12.5-inch barrel and the intended firing schedule. Its outside diameter must fit inside the 1.8-inch-ID handguard.
CM10 Billet Receiver Set
The CM10 upper and lower receivers are CNC-machined from 7075-T6 billet aluminum. The receiver architecture uses the SR25 magazine pattern with DPMS high-profile component compatibility, including the barrel extension, bolt carrier group and 16-TPI barrel-nut interface.
Lightening cuts reduce unnecessary mass while retaining the rigid feel of the billet receiver set. The upper omits the forward assist, and the lower incorporates an integral trigger guard and a machined, widely flared magazine well.
Receiver Features
- 7075-T6 billet-aluminum upper and lower receivers
- SR25-pattern magazine architecture
- DPMS low-profile component compatibility
- 16-TPI barrel-nut interface
- Lightened fire-control and magazine-well surfaces
- Upper-receiver lightening cuts
- No forward assist
- Integral trigger guard
- Machined and flared magazine well
- Fire and Safe markings on both sides
- Ambidextrous safety
- Ambidextrous magazine release
- Ambidextrous bolt release
- CM10 pivot and takedown pins
CM10 Bolt Carrier Group
Bolt Carrier Group Features
- 9310 steel bolt
- High-pressure tested bolt
- Magnetic-particle-inspected bolt
- Shot-peened bolt
- Nitride-coated bolt
- Nitride-coated carrier
- Nitride-coated gas key
- Hardened gas key
- Grade 8 hardened gas-key fasteners
- Properly staked gas key
- Tool-steel extractor
- T.E.A. extractor spring
- Black extractor insert
- Crane O-ring
- Carrier lightening cuts
Upper Operating Components
- CM10 ambidextrous 7075-aluminum charging handle
- Melonite-treated CM gas tube
- Superlative Arms .750-inch adjustable gas block with Melonite treatment
- Adjustable AR10 buffer
TriggerTech AR Duty Trigger
The current CM10 uses a TriggerTech AR Duty trigger rather than the HIPERFIRE trigger referenced in older product descriptions and photographs. Select the available single-stage or two-stage configuration through the product options.
TriggerTech’s zero-creep release provides a clean break and consistent operation. Because the trigger does not use conventional creep to establish a second-stage feel, most CM10 customers select the single-stage option.
B5 Bravo Stock or Pistol Brace
The preferred SBR configuration uses a B5 Systems Bravo stock installed on a carbine receiver extension with multiple adjustment notches. The pistol selection replaces the B5 Bravo stock with an adjustable brace.
Both rear configurations provide the same verified weight, overall-length range and length-of-pull range. The adjustable buffer is a functional part of the 308 Subsonic AR10 operating system, allowing CM to balance carrier movement around the selected ammunition and enclosed suppressor combination.
Dual-Feed LR/SR Magazine System
The CM10 SUBSONIC uses a conventional dual-feed LR/SR-pattern magazine rather than the center-feed AICS system used by specialized CM10 cartridges such as 375 Raptor and 458 SOCOM XL.
One 20-round Magpul PMAG 7.62 is included where permitted. Additional magazines are available through the CM 308 AR10 magazine page.
Compatible Subsonic Ammunition
The CM10 SUBSONIC can stabilize and cycle multiple compatible subsonic loads using projectiles weighing 220 grains and heavier. The adjustable gas block and buffer allow the operating system to be balanced around differences in ammunition and suppressor backpressure.
CM’s 300-grain 308 subsonic ammunition is the verified reference load. It uses a 300-grain Maker REX projectile in new Starline 308 Winchester brass and averages approximately 1,005 feet per second from the 12.5-inch barrel.
The 308 Subsonic AR10 is not limited to the 300-grain load. Other compatible subsonic ammunition using projectiles of 220 grains and heavier can stabilize well in the 1:5 twist and can cycle when the gas system, buffer and enclosed suppressor provide the required operating energy.
CM cannot guarantee identical cycling with every commercial or handloaded subsonic cartridge. Projectile weight, powder selection, pressure curve, cartridge overall length, suppressor design and operating-system adjustment all influence function.
Read the 308 Winchester Subsonic Guide for the complete explanation of projectile stability, barrel twist and semi-automatic cycling.
Supersonic Ammunition Warning
Do not fire supersonic ammunition through the CM10 SUBSONIC. The barrel, gas system, buffer and suppressor requirements were established around subsonic pressure curves. Supersonic ammunition produces substantially different pressure and operating energy and is not supported in this configuration.
Keep supersonic and subsonic 308 Winchester ammunition separated and clearly identified. Use only compatible subsonic ammunition appropriate for the firearm.
308 Subsonic AR10 Dimensions
- Verified weight: 7.5 pounds without accessories
- Verified overall length: 29.25 to 32.5 inches
- Verified length of pull: 11.75 to 15 inches
- Barrel length: 12.5 inches
- Magazine pattern: Dual-feed LR/SR
- Included magazine: One 20-round Magpul PMAG 7.62 where permitted
The verified firearm measurements are the same for the SBR and pistol selections. Any different weight or dimensions displayed elsewhere in the product interface are shipping values.
308 Subsonic AR10 FAQ
Why does CM prefer the SBR configuration?
The B5 Bravo stock and adjustable carbine receiver extension provide a stable shoulder interface while retaining the compact dimensions of the 12.5-inch firearm. Customers can select the pistol configuration if they prefer a brace.
Will this firearm cycle loads other than CM’s 300-grain ammunition?
Yes. The CM10 SUBSONIC can cycle multiple compatible subsonic loads when used with an enclosed suppressor and appropriate gas and buffer settings. Projectiles weighing 220 grains and heavier stabilize well in the 1:5 twist. Changes in ammunition or suppressor may require operating-system adjustment.
Will it cycle subsonic ammunition without a suppressor?
The CM10 SUBSONIC requires an appropriately rated enclosed suppressor to provide the backpressure needed for reliable semi-automatic cycling.
Can I use a flow-through suppressor?
CM does not recommend a flow-through or low-back-pressure suppressor for this firearm. It may release gas too efficiently to operate the action reliably. Use a compatible enclosed, direct-thread suppressor that fits inside the SD handguard.
Can I fire supersonic 308 Winchester ammunition?
No. Supersonic ammunition is not supported in the CM10 SUBSONIC and can be dangerous. Use only compatible subsonic ammunition appropriate for this firearm.
Why does the barrel use a 1:5 twist?
The 1:5 twist stabilizes long, heavy subsonic projectiles weighing 220 grains and heavier. This includes the 2.06-inch 300-grain Maker REX, which is near the upper end of commercially available .308 projectile weight.
Is a suppressor included?
No. A suppressor may be shown in product photographs but is not included. Use an enclosed, 5/8×24 direct-thread suppressor rated for 308 Winchester and the 12.5-inch barrel. Its outside diameter must fit inside the SD handguard.
Does this product include a muzzle device?
No. This configuration is intended for a 5/8×24 direct-thread suppressor and does not include a muzzle-device selection.
What magazines does the firearm use?
The firearm uses dual-feed LR/SR-pattern 308 magazines and includes one 20-round Magpul PMAG 7.62 where permitted.
CM Limited Lifetime Warranty
The CM10 308 Subsonic AR10 is covered by the Chattahoochee Munitions limited lifetime warranty for the original purchaser. Coverage applies to functional operation in the original CM configuration when compatible subsonic ammunition and an enclosed suppressor are used.
Review the complete Chattahoochee Munitions warranty for coverage terms and exclusions.
Reviews
There are no reviews yet.