AR15 Barrel Length and Velocity - WWSD

Published on November 1, 2023
Duration: 7:07

This video explores the impact of AR-15 barrel length on projectile velocity and terminal ballistics using M193 55-grain ammunition. Testing 14.7-inch, 16-inch, and 20-inch barrels with a MagnetoSpeed chronograph, the data reveals significant velocity differences, particularly past 300 yards, affecting accuracy and wounding potential. The discussion also touches on the reliability advantages of longer barrels with rifle-length gas systems.

Quick Summary

AR-15 barrel length significantly impacts 5.56mm M193 velocity and terminal ballistics. Longer barrels (e.g., 20-inch) produce higher velocities (averaging 3037 fps in testing) compared to shorter ones (14.7-inch averaging 2885 fps). This difference is crucial past 300 yards for accuracy and wounding capability.

Chapters

  1. 00:00Introduction: WWSD Variants
  2. 00:26Velocity Dependence of 5.56
  3. 00:44Terminal Ballistics and Velocity
  4. 01:09Ammunition Performance (Mk 262)
  5. 01:33Historical Barrel Lengths and Velocity
  6. 01:59Chronograph Setup and Testing
  7. 02:3514.7-inch Barrel Velocity Data
  8. 03:0716-inch Barrel Velocity Data
  9. 03:3120-inch Barrel Velocity Data
  10. 04:01Data Analysis and Comparison
  11. 04:24Practical Impact Past 300 Yards
  12. 04:49Optimal Barrel Length Conclusion
  13. 05:14Reliability of 20-inch Barrels
  14. 05:41Velocity vs. Handling Trade-offs
  15. 05:53Ammunition Choice Mitigation
  16. 06:20K-Arms WWSD Availability
  17. 06:45Recommendations and Outro

Frequently Asked Questions

How does AR-15 barrel length affect 5.56mm M193 velocity?

Longer AR-15 barrels generally produce higher projectile velocities. Testing showed a 14.7-inch barrel averaging 2885 fps, a 16-inch averaging 2915 fps, and a 20-inch averaging 3037 fps with M193 55-grain ammunition. This velocity difference is most significant past 300 yards.

What is the impact of velocity on terminal ballistics for 5.56mm?

5.56mm, especially older M193 loads, is velocity-dependent for terminal ballistics. Below a certain velocity, rounds can 'ice pick' without adequate cavitation, reducing their effectiveness. Higher initial velocity ensures better performance at range and greater wounding potential.

Is an 18-inch or 20-inch barrel better for an AR-15?

An 18-inch barrel is often considered a good balance of velocity, handling, and control. However, a 20-inch barrel with a rifle-length gas system offers enhanced reliability due to increased dwell time, leading to smoother operation across various ammunition types and environmental conditions.

How can ammunition choice affect AR-15 performance at range?

Using heavier bullets, like 77-grain rounds, with an appropriate barrel twist rate can significantly improve an AR-15's performance at range. This choice helps maintain ballistic coefficient and terminal ballistics, even with slightly lower velocities compared to lighter rounds.

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