CMMG Mk4 Resolute Upper Receiver Group 5.56x45mm NATO 16.1in Armor Black
$849.99 at MidwayUSA · 2 stores
In stock
CMMG Mk4 Endeavor Upper Receiver Group 5.56x45mm NATO 18in Armor Black
No ratings yetBest price
$849.99at OpticsPlanet
Out of stock Sale checked Oct 22, 2026
In stock now instead
- CMMG Mk4 Resolute Upper Receiver Group 5.56x45mm NATO 16.1in Ar… $849.99at MidwayUSA
- Mk4 Banshee Upper Receiver Group, 5.56 NATO, 12.5", Armor Black $819.99at OpticsPlanet
- Brn-601 5.56mm 20" Upper Receiver With Colt 4x21mm Scope $847.99at Brownells
Where to buy
| Store | Price | Availability | Buy | Add to build |
|---|---|---|---|---|
| OpticsPlanet | $849.99Salechecked Oct 22, 2026 | Out of stock | Buy at OpticsPlanet |
Prices and availability change often, so confirm on the store's site before you buy. We may earn a commission from these links.
Similar upper receivers in stock
This part is out of stock at every store we track. These similar upper receivers are in stock, with today's prices.
Mk4 Banshee Upper Receiver Group, 5.56 NATO, 12.5", Armor Black
$819.99 at OpticsPlanet
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Price history
Dashed line = out of stock. Tracking since Oct 14, 2026.
Show the prices as a table
| Store | Latest | Lowest | Highest |
|---|---|---|---|
| OpticsPlanet | $849.99 | $849.99 | $849.99 |
Since Oct 14, 2026.
About this part
The CMMG Mk4 Endeavor Upper Receiver Group 5.56x45mm NATO 18in Armor Black is an 18" 5.56 / .223 upper receiver from CMMG. One store lists it, OpticsPlanet at $849.99.
Fits and works with
- Caliber
- 5.56 / .223 · Shop matching ammo
- Bolt
- Standard AR-15 (5.56 / 300 BLK / .350 Legend) · Bolt carrier groups
- Barrel length
- 18" · Handguards
Specifications
- Manufacturer
- CMMG
- Color
- Black
- Platform
- AR-15
- Caliber
- 5.56 mm NATO
From the manufacturer
CMMG Mk4 Endeavor Upper Receiver Group 5.56x45mm NATO 18in Armor Black. 56mm the ENDEAVOR Mk4 Upper Group is here. Perfect for new builds or for use with an existing AR15 lower receiver this upper utilizes an 18 416 stainless steel barrel with a nitride finish for enhanced ballistic performance and superior durability. Specifications for CMMG Mk4 Endeavor Upper Receiver Group: Manufacturer: CMMG Caliber: 5.56x45mm NATO Overall Length: 26.9 in Barrel Length: 18 in Barrel Profile: Medium Taper Gas System Length: Rifle Length Barrel Twist Rate: 1-7 Muzzle Device: CMMG Zeroed Muzzle Brake Color: Armor Black Fabric/Material: 416SS Gas Block Journal Size-Diameter: .750 in Gun Rail: M-LOK Gun Type: Rifle Gun Make: CMMG Gun Model: CMMG Mk4 Weight: 4.5 lb Magazine Included: No Condition: New Mount Type: M-LOK Threads per Inch: 1/2x28 Package Contents: CMMG Mk4 Endeavor Upper Receiver Group What firearm models does the manufacturer say CMMG Mk4 Endeavor Upper Receiver Group is compatible with? The manufacturer suggests that CMMG Mk4 Endeavor Upper Receiver Group is compatible with CMMG Mk4CMMG 55BFDAB-AB: Mk4 Endeavor Upper Receiver Group 5.56x45mm NATO 18in Armor Black
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