Offset Firing Pin Rimfire Conversion Mechanism
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Solution Overview
Problem
Converting a semi-automatic centerfire rifle to a rimfire caliber while retaining the original fire control group and lower receiver is challenging due to the need for the firing pin to strike the rim of the cartridge instead of the center, requiring a solution that accommodates rimfire cartridges in a design optimized for centerfire cartridges.
Innovation Solution
The semi-automatic rimfire rifle design incorporates a primary and offset firing pin system, where the primary firing pin strikes the offset firing pin to ignite the rimfire cartridge, allowing the use of rimfire ammunition in a rifle originally designed for centerfire cartridges, with a bolt and barrel assembly that maintains the rifle's original fire control group and lower receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a semi-automatic rifle is designed to receive centerfire cartridges, then the fire control group and lower receiver can be optimized for centerfire operation, but the rifle cannot accommodate rimfire cartridges without modification
Solution Approach 1:
The firing pin system is divided into two separate components: a primary firing pin that strikes the offset firing pin, and an offset firing pin that actually contacts the rim of the cartridge. This segmentation allows the primary firing pin to remain aligned with the bolt axis while the offset firing pin contacts the rim at an offset position, enabling rimfire functionality while maintaining the original fire control group design
Solution Approach 2:
The offset firing pin acts as an intermediary between the primary firing pin and the cartridge rim. Instead of the primary firing pin directly striking the rim (which would require realignment of the entire fire control group), the offset firing pin transfers the impact force from the primary firing pin to the cartridge rim, enabling rimfire operation without modifying the lower receiver or fire control group alignment
2Ease of manufacture
If the firing pin is aligned with the bolt axis for centerfire cartridges, then the fire control group design is simplified, but it cannot strike the rim of rimfire cartridges
Solution Approach 1:
The firing pin function is segmented into two separate pins: the primary firing pin maintains alignment with the bolt axis for ease of manufacture and integration with the fire control group, while the offset firing pin is positioned to contact the cartridge rim at the correct offset location. This ensures both manufacturing simplicity and reliable rimfire ignition
Solution Approach 2:
The offset firing pin serves as a mediator that transfers the striking force from the axially-aligned primary firing pin to the offset position on the cartridge rim. This intermediary approach maintains the simplicity of axial alignment in the fire control group while ensuring reliable contact with the rim at the correct position for ignition
3Adaptability or versatility
If rimfire cartridges are used in a centerfire rifle design, then cheaper and less powerful ammunition can be used, but the original fire control group must be modified
Solution Approach 1:
The firing pin system is segmented into a primary firing pin integrated with the fire control group and an offset firing pin that contacts the cartridge rim. This segmentation allows the use of rimfire ammunition in a centerfire rifle design without modifying the lower receiver or fire control group, as the offset firing pin handles the rim contact while the primary firing pin remains part of the original design
Solution Approach 2:
The dual firing pin system provides multi-functionality, allowing the rifle to accommodate both centerfire and rimfire cartridges. The primary firing pin can strike centerfire primers directly, while the offset firing pin is positioned to strike rimfire cartridge rims, enabling the rifle to use different ammunition types without requiring separate fire control groups
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
This design enables the conversion of a semi-automatic centerfire rifle to a rimfire caliber, allowing for the use of less powerful and cheaper ammunition, while ensuring reliable ignition and operation, and reducing manufacturing complexity and stress concentrations through radiused lugs and extractor recesses.
Implementation Method 1
the first firing pin portion being operable to contact the second firing pin portion such that the second firing pin portion discharges a cartridge in response to the first firing pin portion being struck by a hammer
Data Source
AI summary
Semi-automatic rimfire rifles have a frame, a bolt operable to reciprocate within the frame, the bolt defining a bolt axis, the bolt defining a firing pin passage, a first firing pin portion received within at least a first portion of the firing pin passage, a second firing pin portion separate from the first firing pin portion received within at least a second portion of the firing pin passage, and the first firing pin portion being operable to contact the second firing pin portion such that the second firing pin portion discharges a cartridge in response to the first firing pin portion being struck by a hammer. The first firing pin portion may define a first firing pin axis aligned with the bolt axis. The second firing pin portion may have a nose portion that is offset from the bolt axis extending away from the first firing pin portion.