Bolt Hold Open Actuator for Rimfire Firearms
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Solution Overview
Problem
Existing bolt catch mechanisms in firearms, such as AR-15 type firearms, require a magazine follower to hold the bolt open after the last round is fired, limiting functionality with rimfire ammunition and not allowing for a hold open position without a magazine.
Innovation Solution
A bolt catch assembly with an elevatable actuator housing and integrally formed catch component that can be displaced by a follower or used in conjunction with the charging handle to maintain the bolt in an open position, eliminating the need for a magazine follower and enabling operation with rimfire ammunition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a magazine follower is used to hold the bolt open, then the bolt can be held open after the last round is fired, but the system cannot operate with rimfire ammunition and cannot hold open without a magazine
Solution Approach 1:
The patent extracts the bolt hold open function from the magazine follower mechanism and relocates it to an independent actuator assembly. The actuator housing with elevatable catch portion is installed in the receiver independently of the magazine, allowing the bolt to be held open without requiring a magazine follower. This enables operation with rimfire ammunition and without a magazine attached.
Solution Approach 2:
The bolt hold open function is segmented from the magazine assembly and implemented as a separate actuator component. The actuator housing, catch portion, and biasing spring are distinct elements that can operate independently of the magazine follower, providing modular functionality that adapts to different ammunition types and magazine configurations.
2Adaptability or versatility
If the bolt catch actuator is integrated into the receiver, then the bolt can be held open independently of the magazine, but the structure becomes more complex
Solution Approach 1:
The actuator housing is merged with the receiver structure by installing it within the receiver's bolt catch cavity. The actuator components (housing, catch portion, spring) are integrated into the existing receiver architecture, sharing space and structural support with other receiver components. This reduces the overall complexity compared to adding a completely separate external mechanism.
Solution Approach 2:
The actuator assembly serves multiple functions: it provides bolt hold open capability, works with both centerfire and rimfire ammunition, and can operate with or without a magazine attached. The universal design allows a single component to replace multiple specialized mechanisms, actually reducing overall system complexity despite the added integration.
Data Source
AI summary
A bolt hold open (BHOA) catch assembly configured for operating with rimfire ammunition for use with a firearm including a receiver with an exposed receiving chamber. A BHOA housing is supported upon the lower receiver in communication with a receiver chamber in communication with a bolt assembly. A catch is supported in elevatable fashion relative to an end of the actuator housing and an end most and downward extending structural portion of the elevatable catch is capable of being manipulated by an externally configured and toggled bolt catch so that an inner pivoting end portion thereof engages the structural portion to raise the BHOA supported catch into contact with a forwardly traveling bolt, such as upon release of a previously retracted charging handle. The BHOA catch can alternatively be actuated upwardly by a suitably configured follower associated with an attachable and cartridge holding magazine, this again following a last shot hold open protocol.