Hybrid Polymer Lower Receivers with Metal Inserts
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Solution Overview
Problem
Lightweight polymer materials used in firearm receivers lack the strength and durability to withstand the extreme pressures and stresses generated during firing, leading to potential cracking and failure, especially at threaded connections, which increases the risk of firearm malfunction and user injury.
Innovation Solution
Integration of threaded metal inserts made from materials like marine grade brass into polymer lower receiver bodies to reinforce high-stress areas, providing a hybrid polymer-metal receiver that combines the corrosion resistance and light weight of polymers with the strength and durability of metal components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If lightweight polymer materials are used to form firearm receivers, then the weight is reduced and corrosion resistance is improved, but the strength and durability to withstand extreme pressures and stresses are compromised
Solution Approach 1:
The patent applies composite materials by integrating metal threaded inserts (such as stainless steel or aluminum) into the polymer receiver body. This creates a hybrid structure where the polymer provides lightweight and corrosion-resistant properties, while the metal inserts provide the necessary strength and durability to withstand extreme chamber pressures and recoil forces. The composite construction allows the receiver to maintain the advantages of polymer materials while compensating for their strength limitations through strategically placed metal reinforcement elements.
2Ease of manufacture
If polymer materials are used for the receiver body, then manufacturing cost and ease of manufacture are improved, but the ability to withstand extreme chamber pressures is reduced
Solution Approach 1:
The patent applies local quality by providing metal threaded inserts at specific high-stress locations within the polymer receiver, such as the buffer tube thread engagement area and pistol grip screw holes. Rather than making the entire receiver from metal, the reinforcement is localized to where it is most needed. This allows the receiver to maintain ease of polymer manufacturing while ensuring reliability under extreme pressure at critical stress points through targeted metal reinforcement.
3Weight of moving object
If all-polymer receivers are used, then weight is reduced, but the risk of cracking and failure at threaded connections increases
Solution Approach 1:
The patent applies the intermediary principle by introducing metal threaded inserts as mediator elements between the polymer receiver body and the threaded components (buffer tube, pistol grip screw). These metal inserts serve as an intermediate structure that provides robust thread engagement and load-bearing capability, preventing the polymer from directly bearing the high stresses at threaded connections. This intermediary metal layer eliminates the risk of polymer cracking and failure at these critical connection points while maintaining the overall lightweight design.
Data Source
AI summary
Threaded metal inserts for polymer lower receivers and hybrid polymer lower receivers comprising one or more of such inserts, as well as kits and methods therefor are disclosed. A threaded metal insert has a substantially circular aperture configured with screw threads to releasably yet connectively interface with a separate traditionally threaded firearm component such as a buffer tube or a pistol grip screw. Inserts can be any overall shape so long as it can be integrally embedded within a traditionally threaded portion of a polymer lower receiver in a way that does not interfere with normal operation of an assembled firearm and leaves exposed the internal threading of the insert. Inserts can also comprise textural features on the exterior surface configured to permanently interface with and embed the an insert into molded polymer. A hybrid polymer and metal lower receiver is a stripped polymer lower receiver for an AR type firearm, such as the AR-15 or AR-10, having one or more such threaded metal inserts at least partially embedded in a portion thereof.