6mm ARC Upper — CM15 16″
The 6mm ARC Upper from Chattahoochee Munitions combines a lightweight billet receiver, 16″ straight-fluted stainless barrel and mid-length gas system. The configuration includes a Superlative Arms adjustable gas block, with a CM15 low-mass bolt carrier group and Warhammer ambidextrous charging handle available as an optional package.
A 15″ CM M-LOK handguard provides accessory mounting space, while the available muzzle-device selections allow you to choose a suppressor-host device or thread protector. This listing is for the upper assembly; the lower receiver and its components are separate.
A 6mm ARC Upper for Predator Hunting and Range Use
The CM15 brings 6mm ARC to the AR-15 platform for applications including predator hunting and target shooting. The 16″ barrel configuration offers a shorter alternative to the 18″ barrels available on our complete CM15 rifles.
Selecting a 6mm ARC Upper involves the complete firearm configuration. The lower receiver, buffer system, magazine, ammunition and any suppressor all matter to the final combination. Contact CM before ordering if you have questions about pairing this upper with an existing lower.
16″ Fluted 416R Stainless Steel Barrel
The barrel uses 416R stainless steel with an SPR profile, straight fluting and Black Cerakote. Its 1:7 twist rate, mid-length gas system and 5/8×24 muzzle threads match the specifications of this CM15 offering.
This 6mm ARC Upper includes a .750″ gas journal for the supplied adjustable gas block. The barrel specification is 416R stainless steel.
- Chambering: 6mm ARC
- Barrel length: 16″
- Material: 416R stainless steel
- Profile: SPR
- Fluting: Straight
- Finish: Black Cerakote
- Twist rate: 1:7
- Gas system: Mid-length
- Gas journal: .750″
- Muzzle threads: 5/8×24
Superlative Arms Adjustable Gas Block
The 6mm ARC Upper includes a Superlative Arms adjustable gas block paired with a CM Melonite mid-length gas tube. The adjustable gas block is part of the listed upper configuration.
When pairing the upper with a lower receiver, consider the lower’s buffer system and your intended ammunition and suppressor. Contact Chattahoochee Munitions to discuss the complete configuration and any compatibility questions.
- Gas block: Superlative Arms adjustable
- Barrel gas journal: .750″
- Gas tube: CM Melonite
- Gas-system length: Mid-length
Lightweight 6061 Billet Receiver
The CM receiver is machined from 6061 billet aluminum. Reliefs throughout the receiver and a milled channel in the Picatinny rail form the lightweight receiver configuration specified for this upper.
The receiver supplied with this 6mm ARC Upper has its own component specification. It is listed as 6061 billet aluminum, distinct from the 7075-T6 receiver sets specified on our complete CM15 rifles.
15″ CM M-LOK Handguard
The CM 15″ handguard uses 6061 aluminum construction with M-LOK attachment locations for compatible accessories. A full Picatinny top rail provides mounting space, and QD sockets at the 3 and 9 o’clock positions accommodate compatible sling attachments.
- Manufacturer designation: CM
- Length: 15″
- Material: 6061 aluminum
- Accessory interface: M-LOK
- Top rail: Full Picatinny
- QD sockets: 3 and 9 o’clock
Optional CM15 Low-Mass Bolt Carrier Group
The 6mm ARC Upper offers the CM15 low-mass bolt carrier group as part of the optional charging-handle and BCG package. Its specified components include a hardened 9310 steel bolt, 17-4 stainless steel firing pin, and 8620 steel carrier and gas key.
- Bolt: Hardened 9310 steel
- Firing pin: 17-4 stainless steel
- Carrier and gas key: 8620 steel
- Inspection: Magnetic-particle inspected
- Extractor: Hardened S7 tool steel
Optional Warhammer Ambidextrous Charging Handle
The optional CM15 Warhammer ambidextrous charging handle is supplied in collaboration with Breek Arms. Its ambidextrous design provides charging-handle access from either side of the upper.
Select “Yes” under “Charging Handle and Bolt Carrier Group” to include both components. Selecting “No” supplies the upper without the charging handle and bolt carrier group.
Muzzle Device and Suppressor Selection
Choose an available suppressor-host muzzle device or thread protector for the 6mm ARC Upper. Contact CM to confirm your preferred muzzle device, mounting arrangement and any associated price adjustment.
The barrel has 5/8×24 muzzle threads. Suppressor compatibility also requires manufacturer approval for the cartridge, barrel length and mounting system. Our 6mm ARC Suppressor Guide explains the different considerations for CM15 semi-automatic and CM7S bolt-action firearms.
CM15 Magazine Requirements
The CM15 uses an AR-15-pattern magazine for 6mm ARC. The AICS-pattern magazines used by CM7S bolt-action firearms are a different magazine architecture.
See our 6mm ARC AR15 Magazine listing for the magazine Chattahoochee Munitions has vetted for its CM15 configuration. Magazine selection is part of the complete operating system when pairing the upper with a lower receiver.
Part of the Overwatch 6 Lineup
The 6mm ARC Upper is part of Overwatch 6, the Chattahoochee Munitions lineup of complete CM15 and CM7S firearms, CM7S barreled actions and platform-specific magazines.
For a broader comparison of the semi-automatic and bolt-action platforms, barrel configurations and applications, visit our 6mm ARC Rifle Guide.
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