Checking AR-15 Firing Pin Protrusion

Published on December 20, 2019
Duration: 12:46

This guide details four methods for measuring firing pin protrusion on AR-15, M16, and M4 platforms, presented by School of the American Rifle. Proper protrusion is crucial for reliable primer ignition and preventing primer piercing. The methods include using a depth/anvil gauge, a caliper, a specialized firing pin protrusion gauge, and a government-issue style gauge. The recommended range for firing pin protrusion is typically between 0.028" and 0.036".

Quick Summary

Checking AR-15 firing pin protrusion is vital for reliable function. The ideal range is typically 0.028" to 0.036". Too little can cause ignition failures, while too much can pierce primers. Tools like depth gauges, calipers, and specialized firing pin gauges can be used for accurate measurement.

Chapters

  1. 00:00Introduction & Overview of Methods
  2. 00:11Method 1: Depth/Anvil Gauge
  3. 00:55Method 2: Caliper Measurement
  4. 04:47Method 3: Specialized Firing Pin Gauge
  5. 09:34Method 4: Government Issue Style Gauge
  6. 11:47Conclusion & Recap

Frequently Asked Questions

What is the ideal range for AR-15 firing pin protrusion?

The ideal range for AR-15 firing pin protrusion is typically between 0.028 inches and 0.036 inches. A common recommended 'good' range is 0.028" to 0.035" to ensure reliable primer ignition without piercing.

Why is checking firing pin protrusion important for an AR-15?

Checking firing pin protrusion is crucial because too little can prevent the primer from igniting, causing misfires. Conversely, too much protrusion can pierce the primer, leading to malfunctions and potential damage to the firearm.

What tools can be used to measure AR-15 firing pin protrusion?

Several tools can be used, including a digital or analog depth/anvil gauge, a caliper (preferably with a tail), and specialized firing pin protrusion gauges designed for AR platforms. A government-issue style gauge is also demonstrated.

How does a depth gauge measure firing pin protrusion?

To use a depth gauge, you zero it out on the bolt face. Then, you insert the firing pin into the bolt and the gauge will provide a reading indicating how far the firing pin extends beyond the bolt face.

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