Firearm Fire Control Assembly for Open and Closed Bolt Operation
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Solution Overview
Problem
Existing firearms with select-fire capabilities face challenges in balancing accuracy and reliability between open and closed bolt operations, particularly in transitioning between modes, which affects performance and durability, and existing solutions are not adaptable to update existing lower receivers or prevent out-of-battery discharges.
Innovation Solution
A firearm design with a frame and barrel assembly that allows for both closed and open bolt operations, featuring a fire control assembly with a selector switch, bolt sear, and safety sear to manage bolt position and prevent out-of-battery discharges, and includes a sub-frame to support high-stress components, enabling seamless transitions between semi-automatic and fully-automatic modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If open bolt operation is used, then cooling efficiency is improved and cook-off risk is reduced, but accuracy deteriorates and susceptibility to contamination increases
Solution Approach 1:
The firearm system dynamically changes bolt position based on operational mode: open bolt for fully-automatic fire to improve cooling and reduce cook-off, closed bolt for semi-automatic fire to improve accuracy. The selector switch enables this dynamic adaptation between operational states.
2Temperature
If open bolt operation is used, then cooling efficiency is improved, but reliability deteriorates due to increased malfunction risk
Solution Approach 1:
The system dynamically selects bolt operation mode based on firing requirements: open bolt for sustained automatic fire where cooling is prioritized, closed bolt for semi-automatic fire where reliability is prioritized. This dynamic adaptation resolves the reliability-cooling contradiction.
3Measurement precision
If closed bolt operation is used, then accuracy is improved and reliability is enhanced, but cook-off risk increases
Solution Approach 1:
The firearm dynamically adjusts bolt position based on operational context: closed bolt for semi-automatic fire where accuracy is critical, open bolt for fully-automatic fire where cooling is critical. This dynamic adaptation resolves the accuracy-cool- off contradiction.
4Adaptability or versatility
If existing lower receivers are updated with select-fire capability, then adaptability is improved, but structural integrity deteriorates due to stress on thin-walled materials
Solution Approach 1:
A sub-frame structure acts as an intermediary between the fire control assembly and the lower receiver. This sub-frame supports the high-stress fire control components (trigger, selector switch, sears) and transfers their loads to stronger mounting points, protecting the thin-walled lower receiver from damaging stresses while enabling select-fire capability.
Data Source
AI summary
A firearm has a frame with a barrel connected to the frame and defining a barrel axis. The barrel has a rear end defining a chamber, and a bolt assembly reciprocates with respect to the chamber between a closed position adjacent the chamber, and an open position away from the chamber. A fire control assembly includes a trigger and a selector switch with a semi-automatic position and a fully-automatic position. The fire control assembly includes a bolt assembly sear operably engaging the bolt. The fire control assembly operates when the selector switch is in the semi-automatic position in response to pulling the trigger to discharge the firearm, to load a cartridge, and to position the bolt in the closed position. The fire control assembly operates when the selector switch is in the fully-automatic position in response to pulling the trigger to discharge the firearm, and to hold the bolt in the open position. The fire control may include a sub-frame connected to the frame and to the bolt assembly sear, and may include a safety sear that prevents firing out of battery when in either full-auto or semi-auto modes. The fire control system may include a facility that momentarily maintains the trigger in a firing position when it is released while the bolt is moving forward from the open position.