How Does It Work: Lever Delayed Blowback

Published on July 11, 2019
Duration: 2:57

This guide explains the operation of the lever-delayed blowback system, as demonstrated by Ian McCollum of Forgotten Weapons. It details the core components—bolt, bolt carrier, and accelerator lever—and their interaction to create mechanical disadvantage, slowing bolt opening for safe extraction. The explanation highlights how this system manages pressure and its application in submachine guns, noting the necessity of features like fluted chambers for high-pressure cartridges.

Quick Summary

Lever-delayed blowback operates using an accelerator lever to create mechanical disadvantage between the bolt and bolt carrier. This linkage forces the bolt carrier to travel a greater distance than the bolt, slowing its opening speed. This delay allows chamber pressure to drop to a safe level before extraction, and fluted chambers are often used to aid extraction with high-pressure cartridges.

Chapters

  1. 00:00Introduction to Lever Delayed Blowback
  2. 00:20Core Components: Bolt, Carrier, Lever
  3. 00:38Mechanical Disadvantage Principle
  4. 01:13Pressure Management & Delay
  5. 01:50Submachine Gun Application
  6. 02:23Technical Trade-offs: Fluted Chambers

Frequently Asked Questions

How does lever-delayed blowback work?

Lever-delayed blowback uses an accelerator lever to create mechanical disadvantage between the bolt and bolt carrier. When fired, the lever forces the carrier to move further than the bolt, slowing its opening and allowing chamber pressure to drop safely before extraction.

What are the main parts of a lever-delayed blowback system?

The system primarily consists of three parts: the bolt, the bolt carrier, and an accelerator lever. This lever has short and long arms and interacts with the receiver to control the bolt carrier's movement relative to the bolt.

Why are fluted chambers often used with lever-delayed blowback?

High-pressure cartridges in lever-delayed blowback systems can lead to extraction issues due to reduced moving mass. Fluted chambers help facilitate extraction by allowing expanding gases to flow around the cartridge case, preventing it from sticking.

What is the advantage of lever-delayed blowback in submachine guns?

In submachine guns, this system allows for the use of lighter bolt assemblies compared to straight blowback designs. The accelerator lever effectively increases the inertia of the rearward-moving bolt mass, enabling safe operation with less physical weight.

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