The Strangest Accuracy Problem I've Ever Investigated

Published on April 20, 2026
Duration: 12:12

This video investigates an accuracy problem with a Browning XBolt 2 in 6.5 PRC, identifying a 1:7 twist rate as a potential cause for keyholing and poor performance with certain ammunition. The investigation involved testing the twist rate, examining the barrel, and consulting with ammunition manufacturers. The conclusion suggests a combination of an overly fast twist rate and ammunition construction issues led to the observed problems.

Quick Summary

The Browning XBolt 2 in 6.5 PRC experienced keyholing due to an unusually fast 1:7 twist rate, which is faster than the standard 1:8. This excessive twist can cause bullet instability and integrity loss, particularly with certain ammunition types, leading to poor accuracy.

Chapters

  1. 00:00Introduction to the Rifle Accuracy Mystery
  2. 00:51The Beginning of the Mystery: Keyholing
  3. 01:24Identifying the Odd Twist Rate: 1:7
  4. 02:09Testing the Barrel Twist Rate
  5. 03:42Confirmed: 1:7 Twist Rate
  6. 04:07Why 1:7 Twist is Problematic for 6.5 PRC
  7. 05:02Consequences of Over-Stabilization
  8. 05:33Barrel Inspection: Copper Fouling and Tooling Marks
  9. 06:46Slow-Motion and Ballistics Gel Testing
  10. 07:30The End of the Mystery: Manufacturer Responses
  11. 09:03The Culprits: Browning and Remington/Speer
  12. 10:00Conclusion: What Does This Mean?
  13. 11:04Community Browning Rifle Review Event

Frequently Asked Questions

What caused keyholing in the Browning XBolt 2 6.5 PRC?

Keyholing in the Browning XBolt 2 6.5 PRC was primarily caused by an excessively fast 1:7 twist rate in the barrel, which over-stabilized certain bullets, leading to instability and sideways entry into the target. This was exacerbated by the construction of some ammunition, like Remington's Speer bullets.

Is a 1:7 twist rate too fast for a 6.5 PRC?

Yes, a 1:7 twist rate is generally considered too fast for a 6.5 PRC. The standard and recommended twist rate is typically 1:8. While faster twists can stabilize longer bullets, 1:7 can cause issues with bullet integrity and stability at high velocities, especially with cup-and-core ammunition.

What are the consequences of a rifle barrel having too much twist?

Having too much twist in a rifle barrel can lead to over-stabilization, which can cause the jacket and core of cup-and-core bullets to slip or separate. This loss of integrity results in rapid bullet degradation, unpredictable flight, and significant accuracy problems, including keyholing.

How was the twist rate of the Browning XBolt 2 barrel measured?

The twist rate was measured by inserting a cleaning rod into the barrel and marking a piece of duct tape on top. The rod was then pushed through until the tape completed one full 360-degree revolution. The distance between the starting mark and the mark after one revolution was measured to determine the twist rate.

More Reviews Videos You Might Like

More from Backfire

View all →