Chattahoochee Munitions manufactures the CM15 16-inch 6.5 Grendel upper, a complete AR15-pattern upper receiver group that converts a standard AR15 lower to 6.5 Grendel. It pairs a straight-fluted 416R stainless SPR-profile barrel with a 1:8 twist, a mid-length gas system, and a Superlative Arms adjustable gas block, with an optional CM15 Low Mass bolt carrier group manufactured to the Grendel Type II specification.
See every Chattahoochee Munitions 6.5 Grendel rifle, upper, and magazine at Grendel’s Lair, and read the 6.5 Grendel guide for the cartridge background.
Why Choose a 6.5 Grendel Upper
A 6.5 Grendel upper lets you put efficient, high-ballistic-coefficient 6.5mm bullets on the AR15 lower you already own. Compared with 5.56 NATO, the Grendel carries more energy downrange and resists wind better, which suits deer-sized game, feral hogs, predators, and longer-range target shooting. The 16-inch barrel keeps the rifle non-NFA and handy, and the mid-length gas system gives smooth cycling.
Prefer a complete rifle? The complete CM15 6.5 Grendel AR15 comes with 7075-T6 billet receivers, a TriggerTech AR15 Duty trigger, and a B5 Systems stock. The 6.5 Grendel barrel length comparison compares the 16-inch barrel with the 18- and 20-inch CM15 rifles, and our guide to the 6.5 Grendel for coyotes and hogs covers bullets and suppressed setups.
Barrel and Gas System
The 16-inch CM15 barrel is 416R stainless steel in an SPR profile, straight-fluted and finished in E100 Blackout Cerakote, with a 1:8 twist that stabilizes the common range of 6.5 Grendel bullets. It runs a mid-length gas system with a .750-inch gas journal, a Melonite gas tube, and a Superlative Arms adjustable gas block. The 5/8×24 threaded muzzle ships with your choice of muzzle device or a thread protector. Because the CM15 is gas operated, Chattahoochee Munitions recommends a flow-through suppressor to limit back pressure, and the adjustable gas block helps tune the upper for suppressed use.
Upper Receiver, Handguard, and Bolt Carrier Group
The upper receiver is machined from CM 6061 billet aluminum with relief cuts, and the 15-inch CM 6061 M-LOK handguard carries a full-length top Picatinny rail and QD sockets at 3 and 9 o’clock. Order the upper with the optional CM15 Low Mass bolt carrier group, which uses a 9310 steel bolt manufactured to the Grendel Type II specification, and the CM15 Warhammer ambidextrous charging handle made in collaboration with Breek Arms. B5 Systems rail covers come in black or Coyote.
Cerakote Finish Options
Chattahoochee Munitions finishes the receiver and handguard in Cerakote. Choose from eight Cerakote colors: Black Tungsten, Cobalt Kinetics Green, FDE Metallic, Black, FDE, Sniper Grey, OD Green, and Burnt Bronze, or request another single color. Every finish shares the same mechanical specifications.
CM15 16-Inch 6.5 Grendel Upper Specifications
- Manufacturer: Chattahoochee Munitions
- Platform: CM15 AR15-pattern complete upper receiver group, fits a standard AR15 lower receiver
- Chambering: 6.5 Grendel
- Barrel: 16-inch CM15 416R stainless steel, SPR profile, straight-fluted, E100 Blackout Cerakote
- Twist rate: 1:8
- Gas system: Mid-length, .750-inch gas journal, Melonite gas tube
- Gas block: Superlative Arms adjustable
- Muzzle: 5/8×24 threads; choice of muzzle device or thread protector
- Upper receiver: CM 6061 lightweight billet aluminum with relief cuts and milled Picatinny rail
- Handguard: 15-inch CM 6061 M-LOK, full-length top Picatinny rail, QD sockets at 3 and 9 o’clock
- Bolt carrier group (optional): CM15 Low Mass BCG; 9310 steel bolt manufactured to the Grendel Type II specification, MPI tested; 17-4 stainless firing pin; 8620 carrier and gas key; S7 extractor
- Charging handle (optional): CM15 Warhammer ambidextrous charging handle, made in collaboration with Breek Arms; included with the BCG option
- Receiver and handguard finish: Cerakote in Black Tungsten, Cobalt Kinetics Green, FDE Metallic, Black, FDE, Sniper Grey, OD Green, or Burnt Bronze, or another single color on request
- Rail covers: B5 Systems, black or Coyote
- Magazine: 6.5 Grendel AR15-pattern magazine (sold separately)
- NFA status: Non-NFA: the 16-inch barrel requires no tax stamp
Frequently Asked Questions
Who makes a 6.5 Grendel upper?
Chattahoochee Munitions manufactures the CM15 16-inch 6.5 Grendel upper, a complete AR15-pattern upper with a 1:8 twist 416R stainless SPR-profile barrel, mid-length gas, a Superlative Arms adjustable gas block, and an optional CM15 Low Mass bolt carrier group manufactured to the Grendel Type II specification.
Will a 6.5 Grendel upper fit my AR15 lower?
Yes. The CM15 6.5 Grendel upper fits a standard AR15 lower receiver. It needs a 6.5 Grendel AR15-pattern magazine, because standard 5.56 magazines do not feed the larger Grendel case reliably.
Do I need a different bolt for 6.5 Grendel?
Yes. The 6.5 Grendel uses a larger bolt face than 5.56 NATO. Order the upper with the optional CM15 Low Mass BCG, which uses a bolt manufactured to the Grendel Type II specification, or supply a Grendel-specific bolt carrier group.
What does the Cobalt Kinetics Green option mean?
Cobalt Kinetics Green is one of the Cerakote finish colors Chattahoochee Munitions offers for the receiver and handguard. Chattahoochee Munitions manufactures the CM15 upper in every finish.
What twist rate and gas system does it use?
A 1:8 twist and a mid-length gas system with a .750-inch gas journal and a Superlative Arms adjustable gas block.
What suppressor does Chattahoochee Munitions recommend for this upper?
A flow-through suppressor. The CM15 is gas operated, and a flow-through design limits back pressure so the adjustable gas block is easier to tune. Confirm the suppressor is rated for 6.5 Grendel.
What magazine should I use?
A 6.5 Grendel AR15-pattern magazine, such as the 10-round 6.5 Grendel AR15 magazine.
Is the 16-inch upper regulated under the NFA?
No. A 16-inch barrel on a rifle lower is not a short-barreled rifle. Follow federal, state, and local law for your configuration.
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