MPN: 30BC239-AB


  • Compact Action-Direct Impingement System operates without the need for a buffer and buffer tube
  • Caliber: .300 Blackout
  • Finish: Armor Black Cerakote
  • Upper Receiver: CMMG Mk4 Dissent Side Charger Upper Receiver - 7075-T6 Aluminum
  • Handguard: 9.6-Inch CMMG Proprietary Handguard
  • M4 Feed Ramps: Yes
  • Muzzle Device: CMMG .308 ZEROED Linear Compensator
  • Barrel: 10.5" 1:7 Salt Bath Nitrided 4140 Chrome Moly Steel
  • Muzzle Thread Pattern: 5/8"-24
  • Gas Block: .750" Adjustable Gas Block
  • Gas Tube: Pistol-Length Gas Tube
  • Bolt Carrier Group: Dissent Side Charging Bolt
  • Charging Handle: CMMG Dissent Side Charging Handle (Left)
  • HP and MPI Tested

*This upper receiver assembly has a barrel that is shorter than 16". This upper is only for use on AR pistol lower receivers and NFA registered Short-Barreled Rifle (SBR) lower receivers. All NFA laws apply!


  • Weight: ~3.91 lbs.
  • Length: ~19.1"


  • AR-15 lower receiver


  • 1x CMMG Dissent 300 Blackout 10.5" MK4 Complete Side Charging Upper
  • 1x CMMG Dissent Side Charging Bolt
  • 1x 1913 Picatinny Rail End Plate


If you're looking to build a short PDW for personal defense, consider a .300 blackout build. This caliber is designed to offer optimal performance from shorter barrels and has much stopping power.

A Powerhouse in Compact Form

The Dissent 300 Blackout MK4 Complete Side Charging Upper made by CMMG comes with a 10.5-inch barrel and is chambered in the powerful 300 blackout caliber. The barrel on this upper assembly is made from 4140 Chrome Moly Steel, which is more durable than standard stainless steel and offers better heat and corrosion resistance. The barrel is threaded and equipped with a CMMG .308 ZEROED Linear Compensator, the perfect muzzle device for a PDW-style weapon. This upper assembly uses a low-profile pistol-length gas tube, which, along with the barrel, is covered by a 9.6-inch CMMG proprietary handguard. This handguard has M-LOK slots on the bottom and sides and a full-length 1913 Picatinny rail on top.

Revolutionary Design

Unlike ordinary AR pattern rifles, this upper uses a compact action-direct Impingement system. In addition, this system incorporates the recoil spring assembly inside the receiver, eliminating the need for a buffer tube. Therefore, this upper assembly can be used without a buffer tube assembly.

This CMMG Mk4 upper receiver also features a side charging handle on the left. The receiver is made from 7075-T6 Aluminum and comes with a bolt carrier assembly and charging handle. In addition, it uses the specially designed Dissent Side Charging Bolt, and CMMG Dissent Side Charging Handle, both of which work flawlessly with each other to offer an incredible shooting experience.

The barrel, receiver, and bolt carrier group are made from the highest quality materials. They are also HPT and MPI tested to ensure the quality standards that CMMG is known for.

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  • This Item: CMMG Dissent 300 Blackout 10.5" MK4 Complete Side Charging Upper
    MSRP: $1,499.95
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