Bolt Carrier Group Cam Path and Gas Port Optimization
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Solution Overview
Problem
The Stoner Family of Weapons, such as the AR-15, suffer from reliability issues due to excessive friction and fouling, leading to increased operator fatigue and component wear, particularly in adverse conditions, caused by overgassing and inadequate stroke length, resulting in violent bolt unlocking and excessive recoil forces.
Innovation Solution
The solution involves increasing the stroke length of the bolt carrier group and modifying the cam path to reduce friction and fouling, using smaller gas ports, and redesigning components like the gas key and buffer tube to enhance stability and reduce drag, allowing for a more gradual unlocking and locking process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gas port size is increased to improve cycling reliability, then bolt carrier group movement is enhanced, but fouling and friction increase leading to reduced reliability in adverse conditions
Solution Approach 1:
The patent applies parameter changes by optimizing the gas port dimensions to a specific size range that provides sufficient gas pressure to cycle the bolt carrier group reliably while minimizing the amount of gas that causes excessive fouling and friction. This involves precise control of gas port diameter and length parameters to achieve the optimal balance between cycling reliability and fouling reduction.
2Reliability
If stroke length is increased to reduce recoil forces and improve stability, then component wear and operator fatigue decrease, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent implements the nested doll principle by integrating the gas key within the buffer tube structure, where the gas key is positioned inside the buffer tube assembly. This nesting approach allows the stroke length to be extended for reduced recoil and improved stability while avoiding the need for separate external components, thereby managing device complexity through compact integration.
3Object-generated harmful factors
If cam path is modified to enable more gradual unlocking, then friction and fouling are reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies dynamics by designing the cam path with optimized curvature and transition characteristics that enable a more gradual unlocking sequence. The cam path geometry is engineered to progressively engage and disengage the bolt locking surfaces over an extended angular range, reducing impact forces and friction while maintaining manufacturability through reasonable precision tolerances.
4Speed
If gas key and buffer tube are redesigned to reduce drag, then bolt carrier group movement is improved, but component complexity increases
Solution Approach 1:
The patent implements local quality by optimizing specific surface characteristics of the gas key and buffer tube components. This includes applying low-friction coatings to contact surfaces, designing streamlined outer profiles to reduce drag, and selectively roughening or smoothing surfaces in specific areas to control gas flow and minimize resistance, thereby improving movement without requiring complete redesign of entire components.
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 approach reduces the forces applied to firearm components, decreases fouling, and improves reliability and durability, providing a more stable and controlled operation with reduced operator fatigue and extended component life.
Implementation Method 1
The bolt 28 and bolt carrier 26 together act as a piston (bolt 28) and cylinder (bolt cavity or recess within carrier body), which moves as the bolt carrier 26 cavity is filled with gas which pushes the bolt and carrier body apart via expansion of gasses.
Data Source
AI summary
A bolt carrier group assembly and firearm containing a bolt carrier group assembly. The bolt carrier includes a first end closer to a front of the firearm and a second end closer to a rear end of the firearm and configured to slidably engage with a bolt. The bolt is configured to slide within the bolt carrier along a first axis and includes a plurality of lugs at a first end configured to engage with a corresponding plurality of lug receivers of the firearm, wherein the forward most edge of the plurality of lugs defines a bolt face of the bolt. The assembly further includes a cam pin operatively connected to the bolt and a cam slot within which the cam pin is constrained, wherein the cam pin travels along a path defined by the cam slot during rotational and translational movement of the bolt within the bolt carrier causing engagement and disengagement of the plurality of lugs and the lug receivers of the firearm. A distance between the bolt face and a rearward most edge of a bolt catch of a firearm when the bolt carrier is in the rearward most position in the firearm and bolt is at the forward most position within the bolt carrier is at least 0.200 inches.