THE AR FILES | Choosing Barrel Twist and why WE SHOOT the 1:7

Published on October 26, 2023
Duration: 9:27

This guide, presented by a firearms instructor, details the critical relationship between AR-15 barrel twist rates and bullet stabilization. It explains how twist rate affects accuracy with different bullet weights, covers historical context from the M16 to modern ARs, and provides practical advice for selecting the appropriate twist rate for various ammunition types, emphasizing the 1:7 twist's versatility.

Quick Summary

The 1:7 twist rate is a common and versatile choice for AR-15 barrels, particularly for stabilizing heavier 5.56mm projectiles like 77-grain match rounds. While it can also effectively stabilize lighter 55-grain bullets at extended ranges, understanding the relationship between twist rate, bullet weight, and stabilization is crucial for maximizing accuracy.

Chapters

  1. 00:26Introduction to Barrel Twist Rate
  2. 00:55Bullet Flight & Stabilization
  3. 01:25What is Twist Rate?
  4. 02:04Faster vs. Slower Twist
  5. 02:20Evolution of 5.56 Projectiles
  6. 02:44Projectile Length & Twist Rule
  7. 03:00Historical Twist Rates
  8. 03:59Debate on Optimal Stabilization
  9. 04:43Practical Application for 5.56
  10. 05:26Impact of Over-Stabilization
  11. 06:18Consequences of Under-Stabilization
  12. 06:39Why 1:7 is Preferred
  13. 07:29Conclusion: 1:7 for Most Users

Frequently Asked Questions

What is the ideal AR-15 barrel twist rate for 77-grain bullets?

For 77-grain projectiles, a 1:7 twist rate is generally considered optimal for AR-15 barrels. This faster twist ensures sufficient spin to stabilize the longer, heavier bullet, maximizing accuracy at various distances.

Why is a 1:7 twist rate common for AR-15s?

The 1:7 twist rate is common due to its adoption by the military for stabilizing heavier rounds like the M855 and M856. This widespread use, combined with economies of scale in manufacturing, makes it a prevalent and versatile choice for civilian AR-15 owners.

Can a 1:7 twist barrel shoot lighter bullets like 55-grain M193 effectively?

Yes, a 1:7 twist barrel can effectively shoot lighter 55-grain M193 ammunition, even at distances like 500 yards. While theoretically over-spinning lighter bullets might slightly reduce accuracy, the practical impact is often minimal, and the 1:7 twist provides broad compatibility.

What happens if an AR-15 barrel twist rate is too slow for the bullet weight?

If an AR-15 barrel's twist rate is too slow for the bullet's weight and length, the projectile will be under-stabilized. This results in a dramatic loss of accuracy, potential keyholing on targets, and in severe cases, the bullet jacket can separate from the core in flight.

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