.300 Blackout AR Pistol Build

Published on November 7, 2025
Duration: 78:52

This video provides a comprehensive, step-by-step guide to building a .300 Blackout AR pistol. Lead Firearms Instructor Caleb from Brownells demonstrates the installation of various components, including receiver sets, barrels, handguards, triggers, and accessories. The guide emphasizes proper tool usage, torque specifications, and functional checks throughout the build process.

Quick Summary

This video guides you through building a .300 Blackout AR pistol, detailing the installation of Aero Precision receivers, a Ballistic Advantage barrel, Midwest Industries handguard, Sons of Liberty trigger, and various accessories like Surefire lights and Magpul sights.

Chapters

  1. 00:08Introduction & .300 Blackout Build
  2. 00:47Receiver Set: Aero Precision
  3. 01:13Lower Receiver Assembly
  4. 03:50Lower Receiver Tools & Fixtures
  5. 05:04Lower Parts Kit & Pins
  6. 07:19Receiver Extension Installation (BCM)
  7. 10:01Pivot and Take Down Pin Installation
  8. 13:13Castle Nut Staking
  9. 16:36Magazine Catch Installation
  10. 18:44Bolt Catch Installation
  11. 22:32Front Pin (Pivot Pin) Installation
  12. 24:32Grip Installation (Deree Kung Fu)
  13. 25:12Trigger Installation (Sons of Liberty)
  14. 30:15Selector Lever Installation
  15. 33:43Grip Screw Installation
  16. 35:23Brace Installation
  17. 36:15Buffer and Spring Installation
  18. 37:06Upper Receiver Vice Block
  19. 39:39Barrel Installation (Ballistic Advantage)
  20. 40:08Dust Cover Installation
  21. 41:50Forward Assist Installation (LSFA)
  22. 43:29Handguard Installation (Midwest Industries)
  23. 47:25Gas Block & Gas Tube Installation
  24. 55:16Muzzle Device Installation (JMAT Custom)
  25. 58:23Bolt Carrier Group & Charging Handle
  26. 61:24Function Check
  27. 62:29Accessorizing: Grip Stop
  28. 66:34Accessorizing: Weapon Light (Surefire)
  29. 71:44Accessorizing: Rail Panels
  30. 73:02Accessorizing: Backup Sights (Magpul)
  31. 74:39Accessorizing: Optic (Sig Romeo 5)
  32. 77:03Magazine Setup (T-MAG with Deree DOS Boot)
  33. 78:21Final Assembly & Wrap-up

Frequently Asked Questions

What caliber is the AR pistol being built in this video?

The AR pistol being built in this video is chambered in .300 Blackout. This caliber is known for its versatility, particularly for suppressed use and short-barreled applications.

What are the key components used in the .300 Blackout AR pistol build?

Key components include Aero Precision receivers, a Ballistic Advantage barrel, Midwest Industries handguard, Sons of Liberty trigger, BCM recoil system, Surefire weapon light, Magpul sights, and a Sig Sauer Romeo 5 optic.

What is the recommended torque specification for the Midwest Industries Combat HD handguard barrel nut?

For the Midwest Industries Combat HD handguard, the barrel nut should be torqued to 40 foot-pounds, followed by an additional 90 degrees of tightening. The lock screws are then torqued to 40 inch-pounds.

How is the castle nut properly secured on the receiver extension?

The castle nut is secured by threading it onto the receiver extension, then staking it into one of the notches on the extension. This prevents the nut from loosening during operation.

What is the advantage of the Sig Sauer Romeo 5 Gen 2 optic over the Gen 1?

The Sig Sauer Romeo 5 Gen 2 optic features a forged housing, which is a significant improvement over the Gen 1's standard tube housing, offering greater durability and a more robust construction.

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