The amazing 5.7 AR15

Published on October 29, 2023
Duration: 0:44

This guide details the installation of the AR-57 upper receiver onto a standard AR-15 lower receiver, enabling the use of the 5.7x28mm cartridge. It also covers a practical modification using a Magpul PMAG as a brass catcher, demonstrating how spent casings are ejected downward through the AR-15's magazine well. The information is presented with high authority by Military Arms Channel, a recognized firearms reviewer.

Quick Summary

The AR-57 upper receiver converts a standard AR-15 lower to fire the 5.7x28mm cartridge using FN P90 magazines. It features a unique downward ejection system through the AR-15's magazine well. A practical hack involves modifying a Magpul PMAG to catch spent brass effectively.

Chapters

  1. 00:00AR-57 Upper Overview
  2. 00:16Downward Ejection & Brass Catching
  3. 00:34Live Fire Demonstration

Frequently Asked Questions

How does the AR-57 upper receiver work with an AR-15 lower?

The AR-57 upper receiver is designed to pin onto a standard AR-15 lower receiver, allowing you to fire the 5.7x28mm cartridge. It uses FN P90 magazines that mount on top.

What is the unique ejection method of the AR-57 upper?

The AR-57 upper receiver ejects spent 5.7x28mm casings downward through the AR-15's magazine well, which is an unusual but functional design.

How can you catch brass from the AR-57 upper?

A common modification involves using a Magpul PMAG with the top section removed. This modified magazine fits into the AR-15's magazine well and effectively catches the spent brass ejected from the AR-57 upper.

What caliber does the AR-57 upper receiver fire?

The AR-57 upper receiver fires the 5.7x28mm cartridge, a round known for its use in firearms like the FN P90 and FN Five-seveN pistol.

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