Quick Tip: Converting a 5.56 AR-15 to 9mm

Published on April 23, 2019
Duration: 4:19

Converting a 5.56 AR-15 to 9mm involves changing the barrel, bolt, and buffer due to the shift from gas operation to straight blowback. 9mm barrels lack gas ports and locking lugs, while the bolt and buffer must be heavier to manage the blowback force. Adapters are necessary to use pistol magazines, with options like Stern Defense for Glock mags and Hahn Precision for Colt-style mags.

Quick Summary

Converting a 5.56 AR-15 to 9mm requires changing the barrel (no gas port), bolt (heavier), and buffer (dedicated heavy 9mm). Magazine adapters like Stern Defense (Glock) or Hahn Precision (Colt) are needed for pistol magazines.

Chapters

  1. 00:00Intro: 5.56 to 9mm AR-15 Conversion
  2. 00:149mm Barrel Differences (No Gas System)
  3. 00:40Bolt & Buffer Requirements for 9mm Blowback
  4. 01:40Correct 9mm Muzzle Devices
  5. 02:12Magazine Adapters: Stern Defense & Hahn Precision

Frequently Asked Questions

What are the main component changes needed to convert a 5.56 AR-15 to 9mm?

You need to change the barrel to a 9mm version (no gas port), use a dedicated 9mm bolt carrier group, and install a heavier 9mm buffer. A magazine well adapter is also required to use pistol magazines.

Why do 9mm AR-15 barrels differ from 5.56 barrels?

9mm barrels operate via straight blowback, so they lack gas ports, gas blocks, and gas tubes. They also do not have locking lug recesses, as the bolt remains unlocked during firing.

What kind of bolt and buffer are needed for a 9mm AR-15 conversion?

A significantly heavier 9mm bolt carrier group is required to keep the action closed during firing. A dedicated heavy 9mm buffer is also necessary to properly balance the blowback system.

What are the options for using 9mm magazines in an AR-15?

Magazine well adapters are used. Stern Defense adapters typically work with Glock magazines, while Hahn Precision adapters are designed for Colt-style 9mm magazines.

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