CMMG Banshee Mk57
- Category
- Personal Defense Weapon
- Barrel
- 127 mm
- Weight, empty
- 2.18 kg
- Introduced
- 2018
About
What it is, and why it matters
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.
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.
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.
Specification
Everything measured
IdentityWhat it is, who built it and when.
- Manufacturer
- CMMG Inc.
- Category
- Personal Defense Weapon
- Country
- United States
- Status
- In production
- Produced
- 2018
- Variant of
- Caliber variant 5 7x28
DimensionsAs issued, without a magazine or an optic.
- Barrel
- 127 mm
- Overall length
- 531 mm
- Weight, empty
- 2.18 kg
ActionHow it cycles, what trips it, and what feeds it.
- Action
- Delayed blowback
- Firing mechanism
- Hammer fired
- Trigger
- Single stage
- Trigger pull
- 24.0 N
- Capacity
- 20
- Magazine
- Detachable box
MaterialsEach swatch is the material itself, not a colour chosen to stand for it.
- Frame
- Aluminum
- Barrel
- Steel
- Stock
- Polymer
- Finish
- Cerakote
BallisticsFrom the service cartridge, not a handload.
- Muzzle velocity
- 610 m/s
- Muzzle energy
- 470 J
- Effective range
- 100 m
- Maximum range
- 1500 m
Trajectory
What the round does downrange
Solved from the muzzle figures and the bullet. The dashed rule is the effective range on the record, and the crosses are the steps the solver returned.
No load solved for this record yetThe flight path is computed from a cartridge and a bullet. This record has no ammunition filed against its chambering, so there is nothing to solve.
Features
What it has
What the record lists as fitted, drawn from the catalogue.
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
Standing
How it compares
Each figure against the firearms of the same type and cartridge that record it, or of the same type where that cartridge has too few. Positions are read to the nearest tenth.
| Measurement | This firearm | Median | Position |
|---|---|---|---|
| Empty weightAmong 54 personal defense weapons | 2.18 kg | 2.23 kg | Near the median |
| Overall lengthAmong 53 personal defense weapons | 531 mm | 582 mm | Shorter than about 70% |
| Barrel lengthAmong 55 personal defense weapons | 127 mm | 168 mm | Shorter than about 80% |
| Magazine capacityAmong 57 personal defense weapons | 20 | 30 | Holds fewer rounds than about 60% |
Answers
Questions about the CMMG Banshee Mk57
How much does the CMMG Banshee Mk57 weigh?
The CMMG Banshee Mk57 weighs 2.18 kg (4.80 lb) empty.
What caliber is the CMMG Banshee Mk57?
The CMMG Banshee Mk57 is chambered in 5.7x28mm FN.
How many rounds does the CMMG Banshee Mk57 hold?
The CMMG Banshee Mk57 holds 20 rounds, fed from a detachable box magazine.
How long is the CMMG Banshee Mk57?
The CMMG Banshee Mk57 is 531 mm (20.9 in) long overall, with a 127 mm (5.00 in) barrel.
Who makes the CMMG Banshee Mk57?
The CMMG Banshee Mk57 is made by CMMG Inc. (United States).
When was the CMMG Banshee Mk57 introduced?
The CMMG Banshee Mk57 was introduced in 2018.
How does the CMMG Banshee Mk57 operate?
The CMMG Banshee Mk57 uses a delayed blowback action, and its firing mechanism is hammer fired.
Compatibility
Which parts fit this firearm
Studio
Every part that mounts on this, resolved
Not a list the maker typed out: the answer comes from the mounts this firearm exposes and the interface each part needs, so it stays right when either one changes.
- Every part that mounts on any firearm in the catalogue
- Interface standards, platforms and fit overrides
- The same answers through the API and the MCP server
Requires a signed-in GunSpec account on the Studio plan. The answer is computed per part, so it is not part of the public record.
Provenance
What the record holds
Every figure above was taken from one of these pages. The confidence reflects how much of the record came from a page a claim can be checked against.
In service
- Civilian market
- 2018
Provenance
Confidence in this record
85%
Stockists
Where to buy
Offers link straight to the shop. GunSpec never takes the order.
No shop has listed this firearm yet
Stock and prices come from the shops themselves. If you sell this firearm, you can list it and it appears here.
List a firearmMCP
Ask an assistant about it
The same record, reached the way a person asks for it rather than the way a program does.
Ask GunSpec
Works with
Point an MCP client at GunSpec and it answers from the catalogue rather than from memory. A free key covers the read tools.
API
The call that returns this record
The same fields, in the same units, from the same endpoint the page reads.
curl --request GET \ --url 'https://api.gunspec.io/v1/firearms/cmmg-banshee-mk57' \ --header 'X-API-Key: your_key'{ "id": "cmmg-banshee-mk57", "name": "CMMG Banshee Mk57", "manufacturer": { "id": "cmmg", "name": "CMMG Inc.", "countryCode": "US", "foundedYear": 2002, "website": "https://cmmg.com", "logoUrl": null, "description": null, "status": null, "defunctYear": null, "stateOwned": null, "makesFirearms": null, "parentId": null, "predecessorId": null, "createdAt": "2026-02-11 23:44:38", "updatedAt": "2026-02-18 03:43:43", "version": "a7e68de40df3e6e52ce7309f32c551e46f69ca644a4955a2de5291d2bfbf7a0b" }, "category": { "id": "personal-defense-weapon", "name": "Personal Defense Weapon", "description": "Compact firearms designed for non-frontline military personnel" }, "country_of_origin": "US", "year_introduced": 2018, "barrel_length_mm": 127, "weight_empty_g": 2177, "action_type": "delayed_blowback"}