13.7" to 16" : The Best Barrel Length?

Published on November 18, 2024
Duration: 27:04

This video explores the trade-offs of various AR-15 barrel lengths between 13.7 and 16 inches, focusing on velocity, terminal performance, and overall length. The presenter conducted a practical test comparing 13.7", 14.75", 15", and 16" barrels with specific muzzle devices to achieve a 16" legal overall length via pin and weld. Data on velocity, external ballistics (drop), and fragmentation thresholds for M193 ammunition is presented.

Quick Summary

AR-15 barrel lengths between 13.7 and 16 inches offer a balance between compactness and performance. A 13.7" barrel with a pinned muzzle device achieves legal 16" length, while longer barrels like 15" or 16" generally provide higher velocities, impacting bullet drop and terminal ballistics like fragmentation thresholds.

Chapters

  1. 00:06Introduction & Curiosity
  2. 00:34Popularizing the 13.7" Barrel
  3. 01:01Trade-offs in Barrel Length
  4. 01:53Test Setup & Components
  5. 03:50Muzzle Device Options
  6. 04:30Barrel Lengths Tested
  7. 05:06Data Collection Goals
  8. 05:58Testing Methodology
  9. 09:03Velocity Data Results
  10. 11:00External Ballistics (Drop)
  11. 14:03Velocity & Terminal Performance
  12. 17:08Weight Comparison
  13. 18:00Signature Reduction (Flash)
  14. 19:23Flash Signature Testing
  15. 23:12Performance Summary
  16. 23:49Conclusion & Takeaways

Frequently Asked Questions

What is the main advantage of a 13.7-inch AR-15 barrel with a pinned and welded muzzle device?

The primary advantage is achieving a legal 16-inch overall barrel length while maintaining a more compact upper receiver profile, which is beneficial for maneuverability and overall rifle length under NFA regulations.

How does barrel length affect bullet velocity and terminal performance in AR-15s?

Longer barrels generally produce higher muzzle velocities due to more time for powder combustion. This increased velocity impacts external ballistics (like bullet drop) and terminal performance, such as the fragmentation threshold for certain ammunition types like M193.

What is the fragmentation threshold for M193 ammunition?

The generally accepted fragmentation threshold for M193 ammunition is around 2700 feet per second. Velocities below this may result in less consistent or no fragmentation, impacting terminal ballistics.

Does a shorter barrel with a pinned muzzle device weigh less than a standard 16-inch barrel?

In this test, the 13.7-inch upper with a pinned and welded muzzle device weighed slightly less (3 lb 6.7 oz) than the 16-inch upper (3 lb 9.1 oz), indicating that careful selection of muzzle devices can help manage weight.

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