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

Published on July 21, 2022
Duration: 8:03

This video, presented by firearms expert Ian McCollum of Forgotten Weapons, delves into the mechanics and historical application of gain twist (progressive twist) rifling in small arms. McCollum explains how this rifling technique, characterized by an increasing rate of twist from breech to muzzle, aims to improve bullet stability and prevent jacket separation, citing examples from early revolvers to modern high-powered handguns. The discussion highlights its use in specific firearms like the Carcano 1891 and S&W 460 X-frame, while also touching upon its effectiveness and historical context.

Quick Summary

Gain twist (progressive twist) rifling increases the rate of twist from the breech to the muzzle, reducing initial stress on the bullet to prevent jacket separation. Historically used in firearms like the Carcano 1891 and early Colt revolvers, it's also found in modern guns like the S&W 460 X-frame for high-velocity rounds.

Chapters

  1. 00:00Introduction to Gain Twist Rifling
  2. 00:32Defining Gain Twist Rifling
  3. 01:23Purpose and Benefits of Gain Twist
  4. 02:28Historical Examples: Carcano Rifles
  5. 04:16Colt Percussion Revolvers and Gain Twist
  6. 05:34Harry Pope and Custom Barrels
  7. 06:12Modern Applications: S&W 460
  8. 07:01Progressive Depth Rifling Mention

Frequently Asked Questions

What is gain twist rifling?

Gain twist, or progressive twist rifling, is a barrel rifling technique where the rate of twist increases from the breech end of the barrel towards the muzzle. This design aims to reduce initial stress on the bullet.

Why was gain twist rifling used in firearms like the Carcano 1891?

The Carcano 1891 used gain twist rifling primarily to prevent jacket separation from the bullet core, especially with its long 6.5mm bullets. This technique reduces the initial rotational force applied to the projectile.

Are there modern firearms that use gain twist rifling?

Yes, modern firearms like the Smith & Wesson 460 X-frame utilize progressive twist rifling. This helps stabilize high-velocity, large-bore rounds and prevent issues like jacket separation in hand-loaded ammunition.

Does gain twist rifling improve accuracy?

While gain twist can aid bullet stability, historical competition data suggests that standard, constant twist rates often achieve comparable or superior accuracy. Precise barrel manufacturing quality is a significant factor.

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