AR-57

The AR-57, also known as the AR Five Seven, is available as either an upper receiver for the AR-15/M16 rifle or a complete rifle, firing 5.7×28mm rounds from standard FN P90 magazines.

It was designed by AR57 LLC.

Design
The AR-57 PDW upper is a new design on AR-15/M16 rifles, blending the AR-15/M16 lower with a lightweight, monolithic upper receiver system chambered in 5.7×28mm. This model is also sold as a complete rifle, supplied with two 50-round P90 magazines. The magazines mount horizontally on top of the front handguard, with brass ejecting through the magazine well. AR-15/M16-based STANAG magazines can be used to catch spent casings by taking out the feed lips, spring and follower. Sheet metal brass can also be used on the AR-15/M16 lower.

Various scopes and other accessories can be mounted on the picatinny rail.

Unlike the standard AR-15 configuration which uses a gas-tube system, the AR-57 cycles via straight blowback. A fully automatic version exists and was marketed as a competitor to the P90 and other personal defense weapons.

Suppressed versions are also available.

User

 * 🇻🇪 Venezuela (Venezuelan soldiers who defected to Juan Guaidó were photographed using an AR-57 during the crisis in Venezuela in 2019.)