Ask Ian: Progressive Twist (Gain Twist) in Small Arms?

Published on July 21, 2022
Duration: 8:03

This video explores progressive or gain twist rifling, where the rate of rotation changes from breech to muzzle. Historically used in firearms like the Carcano 1891 and early Colt revolvers, its primary benefit is reducing initial bullet stress to prevent jacket separation. While some claim accuracy improvements, historical competition data is mixed. Modern applications include the S&W 460 XVR.

Quick Summary

Gain twist (progressive twist) rifling features a non-constant rate of rotation, starting slow at the breech and accelerating toward the muzzle. Its primary benefit is reducing initial rotational stress on the bullet, preventing jacket separation, though its impact on accuracy is debated.

Chapters

  1. 00:00Intro: Gain Twist Rifling in Small Arms
  2. 00:32What is Gain Twist Rifling?
  3. 01:23Benefits: Preventing Bullet Jacket Separation
  4. 02:28History: Carcano Rifles
  5. 04:16History: Colt Percussion Revolvers
  6. 05:34Custom Barrels: Harry Pope
  7. 06:12Modern Use: S&W 460 X-frame
  8. 07:01Related: Progressive Depth Rifling

Frequently Asked Questions

What is gain twist rifling?

Gain twist (or progressive twist) rifling is a barrel manufacturing technique where the rate of twist changes along the length of the barrel. It typically starts with a slower twist rate near the breech and gradually increases to a faster rate towards the muzzle.

Why was gain twist rifling used historically?

Historically, gain twist rifling was employed to reduce the initial rotational stress on a bullet as it began to spin. This helped prevent the bullet's jacket from separating from its core, especially with longer or softer bullets, and potentially reduced fouling with black powder.

Does gain twist rifling improve accuracy?

While some believe gain twist improves accuracy, historical evidence, particularly from competition shooters, is mixed. Its primary proven benefit is reducing stress on the bullet's construction, preventing jacket separation, rather than consistently enhancing precision.

What are some examples of firearms with gain twist rifling?

Notable examples include the 1891 Carcano military rifle, early Colt percussion revolvers like the Dragoon and 1851 Navy, custom barrels by makers like Harry Pope, and modern firearms such as the Smith & Wesson 460 X-frame revolver.

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