AR57
- Category
- Carbine
- Barrel
- 406 mm
- Weight, empty
- 3.40 kg
- Introduced
- 2010
About
What it is, and why it matters
The AR57 (also marketed as the AR Five Seven) is an American semi-automatic carbine and drop-in upper receiver chambered in 5.7x28mm FN, designed to convert a standard AR-15/M16 lower receiver into a personal defense weapon. It feeds from top-mounted 50-round FN P90 magazines and operates by simple straight blowback rather than the gas-tube system of a conventional AR-15, ejecting spent brass downward through the magazine well. Manufactured by AR57 LLC of Kent, Washington, it is sold both as a complete rifle and as a stand-alone upper.
The AR57 was conceived as a way to bring the FN P90's high-capacity 5.7x28mm package to the ubiquitous AR-15 platform, letting owners reuse their existing lower receivers while feeding from the same translucent 50-round magazines that ride atop the iconic bullpup.
The horizontal P90 magazine mounts atop the handguard and ejection occurs downward through the empty magazine well, giving the AR57 a distinctive ambidextrous, low-blast profile. A short-barreled pistol/PDW configuration is also offered.
Specification
Everything measured
IdentityWhat it is, who built it and when.
- Manufacturer
- AR57 LLC
- Category
- Carbine
- Country
- United States
- Status
- In production
- Produced
- 2010
DimensionsAs issued, without a magazine or an optic.
- Barrel
- 406 mm
- Overall length
- 762 mm
- Weight, empty
- 3.40 kg
ActionHow it cycles, what trips it, and what feeds it.
- Action
- Blowback
- Firing mechanism
- Hammer fired
- Trigger
- Single action
- Capacity
- 50
- Magazine
- Detachable box
MaterialsEach swatch is the material itself, not a colour chosen to stand for it.
- Frame
- Aluminum
- Barrel
- Steel
- Stock
- Aluminum
- Finish
- Anodized
BallisticsFrom the service cartridge, not a handload.
- Muzzle velocity
- 716 m/s
- Muzzle energy
- 534 J
- Effective range
- 100 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.
Top mounted magazine
Picatinny rail
Downward ejection
Non reciprocating charging handle
Ar15 compatible lower
Flash suppressor
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 409 carbines | 3.40 kg | 3.00 kg | Heavier than about 80% |
| Overall lengthAmong 407 carbines | 762 mm | 895 mm | Shorter than about 90% |
| Barrel lengthAmong 423 carbines | 406 mm | 406 mm | Shorter than about 60% |
| Magazine capacityAmong 423 carbines | 50 | 21 | Holds more rounds than about 90% |
Its place in the rankings
Answers
Questions about the AR57
How much does the AR57 weigh?
The AR57 weighs 3.40 kg (7.50 lb) empty.
What caliber is the AR57?
The AR57 is chambered in 5.7x28mm FN.
How many rounds does the AR57 hold?
The AR57 holds 50 rounds, fed from a detachable box magazine.
How long is the AR57?
The AR57 is 762 mm (30.0 in) long overall, with a 406 mm (16.0 in) barrel.
Who makes the AR57?
The AR57 is made by AR57 LLC (United States). It was designed by AR57 LLC.
When was the AR57 introduced?
The AR57 was introduced in 2010.
How does the AR57 operate?
The AR57 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.
Provenance
Confidence in this record
78%
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/ar57' \ --header 'X-API-Key: your_key'{ "id": "ar57", "name": "AR57", "manufacturer": { "id": "ar57", "name": "AR57 LLC", "countryCode": "US", "foundedYear": null, "website": null, "logoUrl": null, "description": null, "status": null, "defunctYear": null, "stateOwned": null, "makesFirearms": null, "parentId": null, "predecessorId": null, "createdAt": "2026-06-21 23:00:46", "updatedAt": "2026-06-21 23:00:46", "version": "4b79c8d8546343ba878cd50c1b5fca76f9667b2787b37561e13ffb24680b23ca" }, "category": { "id": "carbine", "name": "Carbine", "description": "Shortened rifles for close-quarters use" }, "country_of_origin": "US", "year_introduced": 2010, "barrel_length_mm": 406, "weight_empty_g": 3400, "action_type": "blowback"}