This Almost DESTROYED My AR Pistol Build

Published on November 9, 2021
Duration: 21:17

This video details troubleshooting a .300 Blackout AR pistol build that suffered from undergassing and hammer follow. The issues were resolved by swapping the trigger to a Geissele SD-3G, then a Faxon skeletonized BCG, and finally by precisely realigning the gas port and gas block, which was found to be the root cause due to a tolerance stack issue between brands.

Quick Summary

Hammer follow in AR pistols is a safety hazard caused by trigger group tolerance issues. Undergassing can be fixed by reducing reciprocating mass with a lightweight BCG or ensuring proper gas port alignment. Tolerance stacking between components can lead to critical malfunctions.

Chapters

  1. 00:00Intro & Build Overview
  2. 01:26Handguard & Brace Features
  3. 02:31Cycling & Hammer Follow Issues
  4. 05:14Trigger & BCG Troubleshooting
  5. 09:12Root Cause: Gas Port Alignment
  6. 11:13DIY Fix & Final Testing
  7. 14:59Optics & Magazine Compatibility

Frequently Asked Questions

What causes hammer follow in an AR pistol build?

Hammer follow in an AR pistol can be caused by tolerance issues between the drop-in trigger unit and the receiver set, preventing the hammer from resetting properly after firing. This is a critical safety concern that requires immediate attention and potential component replacement.

How can undergassing in an AR pistol be fixed?

Undergassing can be addressed by ensuring the gas block is properly aligned and the gas port is clear. If the system is still under-gassed, reducing reciprocating mass with a lightweight bolt carrier group (BCG) is a common solution, especially if the buffer system cannot be easily modified.

What is tolerance stacking in firearm builds?

Tolerance stacking refers to the cumulative effect of variations in the dimensions of individual parts. When multiple parts with slight deviations are assembled, their combined tolerances can lead to significant issues, such as misaligned gas ports, affecting firearm function and reliability.

What is the function of a lightweight BCG in an AR build?

A lightweight bolt carrier group (BCG) reduces the reciprocating mass within an AR-15 system. This can help resolve undergassing issues by allowing the bolt to cycle more efficiently, ensuring proper function, especially in shorter-barreled or pistol builds where gas pressure might be marginal.

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