• Radial Delayed Blowback System - softer recoil impulse and reduced bolt weight
  • Caliber: 9mm
  • Finish: Armor Black Cerakote, Sniper Grey, or Coyote Tan
  • Upper Receiver: CMMG Mk4 Upper Receiver - 6061-T6 Aluminum
  • Handguard: 4-Inch CMMG EML7 Handguard
  • Muzzle Device: CMMG 9mm ZEROED Linear Compensator
  • Barrel: 5" 1:10 Salt Bath Nitrided 4140 Chrome Moly Steel
  • Muzzle Thread Pattern: 1/2"-28
  • Bolt Carrier Group: CMMG 9mm MkGs Bolt Carrier Group
  • Charging Handle: CMMG ZEROED AR15 Ambi Charging Handle
  • 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: ~2.53 lbs.
  • Length: ~13.31"


  • AR-15 lower receiver with AR9 conversion magazine
  • CMMG Mk9 lower receiver with Colt-pattern magazine
  • CMMG MkGs lower receiver with Glock-pattern magazine
  • CMMG Mk17 lower receiver with Sig P320 magazine


  • 1x CMMG Banshee 9mm 5" MK4 Complete Upper
  • 1x CMMG 9mm MkGs Bolt Carrier Group
  • 1x CMMG ZEROED AR15 Ambi Charging Handle


The CMMG Banshee is one of the most popular 9mm Pistol Caliber Carbines on the market. It is super reliable and makes for an excellent home defense weapon or PDW.

Here we have the CMMG Banshee MK4 9mm complete upper assembly. This upper assembly comes with a 5-inch barrel made from Salt Bath Nitrided 4140 Chrome Moly Steel, making it durable and giving excellent performance even at high temperatures.

The barrel has a 1:10 twist rifling profile, ideal for a wide range of 9mm bullets and works exceptionally well at stabilizing standard 115 grain 9mm bullets. With the small 5-inch barrel, you can expect a lot of muzzle flash from this upper; therefore, it comes equipped with a CMMG 9mm ZEROED Linear Compensator, which significantly decreases perceived recoil and muzzle flip, improving the overall performance of your PCC.

The CMMG Banshee Mk4 Uppers are different from most blowback 9mm uppers. They use a Radial Delayed Blowback system instead of straight blowback. This allows them to use a lighter bolt and have a significantly softer recoil impulse. It comes with a CMMG 9mm MkGs Bolt Carrier Group, which is compatible with all 9mm AR lowers, whether they use Colt-style or Glock-style magazines. With this upper assembly, you also get a CMMG ZEROED AR15 Ambidextrous Charging Handle.

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  • This Item: CMMG Banshee 9mm 5" MK4 Complete Upper
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