CMMG Banshee Mk57
CMMG Inc. · Personal Defense Weapon · In Production · 2018
Also known as: Banshee 5.7, Mk57 Banshee, CMMG Mk57
Overview
The CMMG Banshee Mk57 is an AR-pattern personal defense weapon pistol/SBR chambered in 5.7x28mm FN, built around CMMG's proprietary patent-pending Radial Delayed Blowback action. The platform accepts standard FN Five-seveN pistol magazines (20-round and 30-round), making it a popular companion to the FN Five-seveN handgun. Configurations include 5-inch and 8-inch barrels in pistol (Tailhook MOD 2 / RipBrace) and SBR (RipStock) formats. Built with a 6061-T6 billet aluminum upper, 7075-T6 forged aluminum lower, 4140 chrome-moly steel barrel with SBN nitride finish, and Cerakote finish in multiple color options.
Specifications
| Weight (empty) | 2177 g (76.8 oz) |
| Overall Length | 531 mm (20.91") |
| Barrel Length | 127 mm (5.00") |
| Action Type | Delayed Blowback |
| Firing Mechanism | Hammer Fired |
| Trigger Type | Single Stage |
| Trigger Pull | 24 N (5.4 lbf) |
| Magazine Capacity | 20 rounds |
| Magazine Type | Detachable Box |
| Muzzle Velocity | 610 m/s (2001 fps) |
| Muzzle Energy | 470 J (347 ft·lbf) |
| Effective Range | 100 m (109 yd) |
| Maximum Range | 1500 m (1640 yd) |
| Barrel Rifling | Right Hand |
| Rifling Twist | 229 mm (9.02") |
| Frame Material | Aluminum |
| Barrel Material | Steel |
| Stock Material | Polymer |
| Finish | Cerakote |
Calibers
- 5.7x28mm FN · primary — also known as 5.7x28, FN 5.7
Features
- Firing modes: Semi Automatic
- Feed systems: Detachable Box Magazine Fn Five Seven Pattern 20rd, Detachable Box Magazine Fn Five Seven Pattern 30rd
- Safety mechanisms: Ambidextrous Ar15 Selector, Manual Safety
- Features: Radial Delayed Blowback, Ar15 Pattern, Ambidextrous Controls, Ambidextrous Charging Handle, Ambidextrous Bolt Catch, M Lok Handguard, 1 2x28 Threaded Muzzle, Linear Compensator, Suppressor Compatible, Last Round Bolt Hold Open, Oversized Magazine Release, Ripbrace Or Tailhook Mod 2, Fn Five Seven Magazine Compatible
Variants
- Banshee Mk57 Pistol 8" — Barrel Length
- Banshee Mk57 SBR 5" — Nfa Sbr
- Banshee Mk57 SBR 8" — Nfa Sbr
- Mk4 5.7 — Rifle Sister Model
Base model
Service history
Operators
- Civilian market · adopted 2018 · as Banshee Mk57
Production
Production years: 2018-present
Civilian-market firearm. No documented military or law enforcement adoption.
Origin
Country of origin: United States
Notes
Radial Delayed Blowback uses a rotating bolt head to mechanically delay unlocking - closest schema enum is `delayed_blowback`. The 100/200/300 series tier naming applies to CMMG's other Banshee chamberings (9mm/.300 BLK/.45 ACP); the Mk57 line is organized by pistol-vs-SBR and barrel length rather than tier. Manufacturer lists 4.8 lb (~2177 g); TFB measured 4.7 lb (~2132 g). Year introduced is 2018, not later - TFB review published September 2018 and Shooting Illustrated explicitly states 2018.
Background
CMMG developed its proprietary Radial Delayed Blowback specifically to tame the high-pressure 5.7x28mm cartridge inside an AR-15 host - a chambering otherwise dominated by FN's PS90 and Five-seveN. The Mk57 was one of the first commercially successful non-FN platforms to chamber 5.7x28mm and was designed from the start to share magazines with the Five-seveN pistol.