CMMG MK4 .300BLK Banshee Upper Group Receiver 8in 1-7 Twist 5/8 X 24 TPI 16.5in Armor Black
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CMMG
Overview
The CMMG Mk4 .300BLK Banshee Upper Group Receiver features a complete assembly designed specifically for the AR-15 platform. With an 8-inch barrel and a 1:7 twist rate, this upper is optimized for the .300 Blackout caliber, allowing for effective stabilization of heavier projectiles, making it suitable for both supersonic and subsonic ammunition. Commonly found in builds focused on .300 Blackout, this upper receiver is an excellent choice for those looking to maximize versatility and performance in a compact format.
Specifications
CMMG MK4 .300BLK Banshee Upper Group Receiver 8in 1-7 Twist 5/8 X 24 TPI 16.5in Armor Black
September 2026 on GunPartPicker
CMMG MK4 .300BLK Banshee Upper Group Receiver 8in 1-7 Twist 5/8 X 24 TPI 16.5in Armor Black ranked #66 of the 615 upper receivers builders added on GunPartPicker in September 2026. Builders have been adding it to their builds on GunPartPicker since February 2026. All time, it ranks #102 of the 1,642 upper receivers builders have added. Builds with this upper receiver are nearly all chambered in 300 Blackout, nearly all on pistol-length gas, and nearly all AR-15.
It was hard to find in September 2026, in stock on only 4 of the 8 days we checked, and today only Optics Planet has it in stock. Prices barely moved in September 2026, holding around $660.23, so there haven't been real sales lately. Buying today, the lowest price is $789.99 at Optics Planet, above September's low of $660.23, so a better deal may come back.
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