Compact Roller-Lock Delayed Blowback Mechanism for Semi-Automatic Shotguns
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Solution Overview
Problem
Existing semi-automatic shotgun designs face challenges in implementing a delayed blowback action system due to the large diameter of shotgun cartridges, which requires a bulky mechanism interfering with feeding and ejecting processes, and existing systems provide constant resistance unsuitable for varying ammunition sizes and types.
Innovation Solution
A compact roller-lock delayed blowback mechanism with a primary roller-lock mechanism located rearward of the feeding and ejecting ports, and an optional secondary mechanism, utilizing arcuate geometry surfaces to provide variable resistance to the bolt and bolt carrier, allowing for efficient operation across a range of ammunition sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional roller-lock delayed blowback mechanism is used in a shotgun, then the mechanism provides reliable delayed blowback action, but the large diameter of shotgun cartridges requires a bulky mechanism that interferes with feeding and ejecting processes
Solution Approach 1:
The patent relocates the roller-lock mechanism from a longitudinal arrangement (within the bolt) to a transverse arrangement (at the rear of the action, perpendicular to the bolt axis). This dimensional change allows the mechanism to fit within the clearance space behind the ejection port rather than competing for longitudinal space, thereby reducing interference with feeding and ejecting processes while maintaining the delayed blowback function
Solution Approach 2:
The patent divides the roller-lock mechanism into separate components: the rollers are positioned in a stationary housing behind the ejection port, while the bolt carrier contains the cam surfaces that actuate the rollers. This segmentation allows each component to be optimized independently and reduces the overall volume required for the mechanism by eliminating the need for a large caged bolt
2Adaptability or versatility
If a constant resistance roller-lock mechanism is used, then the mechanism provides simple and reliable operation, but it cannot accommodate a wide range of ammunition sizes and types
Solution Approach 1:
The patent replaces the constant resistance mechanism with dynamic, adjustable resistance provided by spring-loaded cam surfaces. The cam surfaces can be adjusted to vary the resistance applied to the bolt carrier, allowing the same mechanism to accommodate different ammunition types and sizes by changing the cam geometry or spring tension rather than requiring multiple fixed-resistance mechanisms
Solution Approach 2:
The patent enables variation of the resistance parameter through adjustable cam surfaces with different geometries or positions. By changing the cam profile or its position relative to the bolt carrier, the resistance characteristics can be modified to match different ammunition types, providing adaptability without requiring completely different mechanisms for each ammunition type
3Reliability
If the roller-lock mechanism is positioned within the bolt, then the mechanism provides adequate delay, but the bolt becomes necessarily larger, heavier, and more resistant to acceleration
Solution Approach 1:
The patent extracts the roller-lock mechanism from the bolt and relocates it to a stationary housing behind the ejection port. This extraction eliminates the need for the bolt to contain large roller cages, thereby reducing the bolt's weight and moment of inertia. The delay function is maintained through the interaction between the bolt carrier's cam surfaces and the stationary rollers, achieving the same delay effect with lighter moving parts
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables a lightweight, low-maintenance, and reliable action system that effectively delays the opening of the firearm chamber until explosive pressure is reduced, accommodating a wide range of ammunition types without excessive inertial resistance, ensuring safe and reliable operation.
Implementation Method 1
the inertia of a relatively lesser mass (the firing pin and striking hammer) sufficiently delays the opening of the firing chamber until the explosive pressure within is reduced to a safe level by retarding the movement of the bolt carrier relative to the bolt
Implementation Method 2
A surface is attached to the bolt carrier or the receiver, and, a roller is positioned rearward of the ejection port and proximate the surface
Data Source
AI summary
A method and apparatus providing an action system for a semi-automatic shotgun including a receiver having an ejection port for expelling an empty cartridge of a fired projectile. The action system includes a bolt attached to a bolt carrier, wherein the bolt and the bolt carrier are movable within the receiver and substantially parallel to a longitudinal axis. A surface is attached to at least the bolt carrier or the receiver, and a roller is positioned rearward of the ejection port and proximate the surface, wherein a resistance is provided to rearward movement of at least the bolt or bolt carrier.