CMMG Banshee 300
- Category
- Personal Defense Weapon
- Barrel
- 127 mm
- Weight, empty
- 2.13 kg
- Introduced
- 2019
About
What it is, and why it matters
The CMMG Banshee 300 is an AR-pattern pistol-caliber personal-defense weapon, the mid-tier model of CMMG's Banshee line, built around a 5-inch (127 mm) threaded barrel. In its primary 9x19mm chambering it uses CMMG's patented Radial Delayed Blowback operating system: the bolt resembles an AR-15 bolt carrier group but has cammed locking-lug cuts that briefly delay unlocking, allowing a lighter buffer and reciprocating mass than conventional straight blowback and yielding softer, more controllable recoil. The 9mm Mk9/MkGs models feed from Glock-pattern or SIG-pattern magazines respectively, and the platform retains familiar AR-15 ergonomics and a free-floating M-LOK handguard. The Banshee 300 is also offered in 10mm Auto (Mk10) and 7.62x39mm (Mk47), among other chamberings, and ships as a braced pistol with CMMG's adjustable RipBrace.
CMMG's Radial Delayed Blowback was an attempt to fix the AR pistol-caliber carbine's biggest flaw - the heavy, jarring bolt of straight blowback - by machining delay lugs onto an otherwise AR-style bolt, letting the Banshee shoot like a tuned gas gun while staying a simple, magazine-flexible PCC.
Radial Delayed Blowback is CMMG's signature operating system and the key differentiator from simple-blowback PCC pistols; it is the reason the Banshee runs lighter buffers and shoots flatter than typical 9mm AR-pattern guns. The Banshee line is tiered as the 100 (entry), 200 (mid), and 300 (premium-feature) series; the 300 adds ambidextrous controls and a higher-spec trigger. The standard 9mm models use Glock-pattern (Mk9) or SIG P320/MPX-pattern (MkGs) magazines depending on configuration. Empty weight is approximate and varies by configuration.
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
- 2019
DimensionsAs issued, without a magazine or an optic.
- Barrel
- 127 mm
- Weight, empty
- 2.13 kg
ActionHow it cycles, what trips it, and what feeds it.
- Action
- Blowback
- Firing mechanism
- Hammer fired
- Trigger
- Single stage
- Capacity
- 30
- Magazine
- Detachable box
MaterialsEach swatch is the material itself, not a colour chosen to stand for it.
- Frame
- Aluminum
- Barrel
- Steel
- Finish
- Hard coat anodized
BallisticsFrom the service cartridge, not a handload.
- Muzzle velocity
- 396 m/s
- Muzzle energy
- 584 J
- Effective range
- 75 m
- Maximum range
- 150 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.
Features
What it has
What the record lists as fitted, drawn from the catalogue.
Radial delayed blowback
Ar15 style controls
M-lok handguard
Free floating barrel
Picatinny rail- Ripbrace adjustable
Threaded barrel
Glock magazine compatible
Suppressor ready
Ambidextrous controls
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 | 2.13 kg | 2.23 kg | Lighter than about 60% |
| Barrel lengthAmong 55 personal defense weapons | 127 mm | 168 mm | Shorter than about 80% |
| Magazine capacityAmong 25 9x19mm Parabellum personal defense weapons | 30 | 20 | Holds more rounds than about 70% |
Answers
Questions about the CMMG Banshee 300
How much does the CMMG Banshee 300 weigh?
The CMMG Banshee 300 weighs 2.13 kg (4.69 lb) empty.
What caliber is the CMMG Banshee 300?
The CMMG Banshee 300 is chambered in 9x19mm Parabellum.
How many rounds does the CMMG Banshee 300 hold?
The CMMG Banshee 300 holds 30 rounds, fed from a detachable box magazine.
How long is the CMMG Banshee 300?
The CMMG Banshee 300 has a 127 mm (5.00 in) barrel.
Who makes the CMMG Banshee 300?
The CMMG Banshee 300 is made by CMMG Inc. (United States). It was designed by CMMG engineering team.
When was the CMMG Banshee 300 introduced?
The CMMG Banshee 300 was introduced in 2019.
How does the CMMG Banshee 300 operate?
The CMMG Banshee 300 uses a 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 (United States)
- United States
Provenance
Confidence in this record
68%
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-300' \ --header 'X-API-Key: your_key'{ "id": "cmmg-banshee-300", "name": "CMMG Banshee 300", "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": 2019, "barrel_length_mm": 127, "weight_empty_g": 2126, "action_type": "blowback"}