Smyth Busters: Large-Caliber ARs Need Heavy Hammer Springs?

Published on October 11, 2022
Duration: 6:21

This guide addresses the myth that large-caliber AR platforms require heavier hammer springs. Experts Steven and Caleb from Brownells explain that the issue is typically related to primer hardness, not caliber size. Specifically, AR-15s chambered in 7.62x39mm often experience light primer strikes due to hard Russian primers, exacerbated by light aftermarket hammer springs and low-mass firing pins. Solutions involve using heavier power hammer springs, full-mass hammers, and beefier firing pins.

Quick Summary

Large-caliber AR platforms do not inherently require heavier hammer springs; the issue is typically primer hardness. For AR-15s, especially in 7.62x39mm, hard primers can cause light strikes if using light aftermarket hammer springs or low-mass firing pins. Solutions include heavier hammer springs and beefier firing pins.

Chapters

  1. 00:03Introduction & Myth Topic
  2. 00:15Clarifying Large Calibers
  3. 01:27Reloading & Primer Types
  4. 01:40Myth Origin Hypothesis
  5. 02:267.62x39mm & Light Strikes
  6. 02:40AR-15 Firing Pin/Hammer Spring Issues
  7. 03:36Addressing 7.62x39mm AR-15s
  8. 05:04AR-15 Match Springs in AR-308
  9. 05:17Myth Debunked: Hammer Springs for Large Calibers
  10. 05:37Standard Hammer Spring Efficacy

Frequently Asked Questions

Do large-caliber AR-15s require heavier hammer springs?

No, large-caliber AR platforms do not inherently require heavier hammer springs. The issue of primer ignition is more closely related to the hardness of the primer itself, especially in calibers like 7.62x39mm, rather than the caliber's size.

What causes light primer strikes in AR-15s, especially with 7.62x39mm?

Light primer strikes in AR-15s, particularly with 7.62x39mm, are often caused by hard primers combined with light aftermarket hammer springs or low-mass firing pins. These components may not deliver sufficient impact energy for reliable ignition.

How can I fix light primer strikes in my 7.62x39mm AR-15?

To fix light primer strikes in a 7.62x39mm AR-15, consider upgrading to a heavier power hammer spring (like a Wolf spring), a full-mass hammer without lightning cuts, and a beefier firing pin for increased impact energy.

What's the difference between AR-15 and AR-308 primer types?

AR-15 platforms typically use small rifle primers, while AR-308 platforms utilize large rifle primers. This difference is a component specification and not the primary reason for needing heavier hammer springs based on caliber.

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