CMMG MK57 Banshee 300 (5.7x28mm) Semi-Auto Pistol (Black) with Aero Precision M4E1 Lower Receiver & SBA3 Pistol Brace

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“Say hello to my little friend!”


CMMG delivers its lightest and most compact firearms within the BANSHEE line of AR pistols. Don’t let this little guy fool you though, chambered in 5.7x28mm, there’s plenty of firepower in this BANSHEE 300 pistol.  Combined with an Aero Precision M4E1 lower receiver, this BANSHEE will accept the CMMG 5.7 conversion magazines.  From plinking at the range with friends, to competition shooting, to serious personal protection. This Banshee 300 has you covered.

The Aero Banshee 5.7×28 comes with:

  • Aero Precision M4E1 lower receiver
  • CMMG Banshee 300 MK57
  • 5″ barrel (the shortest barrel in 5.7x28mm)
  • Compact Receiver Extension and Compact Stock
  • RML Handguard -Premiere Cerakote finish standard
  • Ambi Charging Handle
  • Magpul MOE Pistol Grip
  • SB Tactical SBA3 Pistol Brace

Aero Precision M4E1

The M4E1 Lower Receiver delivers billet aesthetics in a forged package. This custom designed enhanced forging is machined from 7075-T6 Aluminum and compatible with all mil-spec AR15 parts. Aside from the visual upgrades this custom engineered design provides that challenge much more expensive billet options, Aero Precision has added several functional features to the lower receiver to simplify the assembly process for the at home builder.

M4E1 Lower Features:

  • Threaded Bolt Catch Roll Pin – Allows for simple installation of the bolt catch and virtually eliminates the chance to damage the finish during installation (pin included). 1/16″ Hex Key required for assembly.
  • Integrated Trigger Guard – Eliminates the possibility of breaking the trigger guard tabs by integrating the trigger guard into the lower, creating a stronger more rigid platform to build upon.
  • Upper Tension Screw – Allows users to fine tune the fit of the upper and lower receiver using a nylon tipped tensioning set screw inserted in the grip tang of the lower receiver. This provides a tight fit with any standard AR15 upper receiver.
  • Threaded Takedown Pin Detent Recess – Allows user to easily install the Takedown Pin detent and spring with the use of a 4-40 set screw (no more launching detents across the room).
  • Increased Magwell Flare – Increased the flare of the magwell to aid in quick and efficient magazine changes.
  • Marked and milled to accept short-throw safety selectors, but will work with standard selectors as well.
SKU: 47927 Categories: , Tag:


Additional Information
ManufacturerAero Precision Lower – CMMG Upper
ModelM4E1 Lower – Banshee 300 Upper
TypePistol:  Semi-Auto
ReceiverBlack Billet 7075-T6 Aluminum
Handguard4″ M-LOK CMMG Rail
SightsSights not included
Barrel Length5″  (1:9 Twist) Threaded 1/2×28
Overall Length19.2″
Weight4.5 lbs
MagazinesOne 40-Round CMMG 5.7 Conversion Magazine
Pistol BraceSB Tactical SBA3 Pistol Brace
Product SKUM4E1-54F18E9

Additional Information Content

Modern Warriors

We started Modern Warriors for the sole purpose of providing a less expensive way to enjoy our love of buying and shooting some really cool stuff. What started as a hobby has turned into a business where we have developed the experience and ability to help you enjoy our same hobby and save you money in the process.

We specialize in tactical weapons, including suppressors, short barrel rifles and full auto weapons. We have routine experience in shooting the weapons we carry, so if you want our opinion on how a weapon operates, we will gladly provide it. We also have expertise working with licensed professionals in setting up gun trusts, which is an ideal way of purchasing, owning and operating any weapon restricted by the National Firearm Act. Don’t let the word “trust” scare you. It is very easy to set one up if you have the right help.

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