Pump Action Rifle Lock Mechanism
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Solution Overview
Problem
Modern sporting rifles require an effective action locking mechanism that reliably locks the bolt carrier in the forward position and unlocks it after firing to cycle the firearm, while being insensitive to ammunition quality and compliant with regulatory requirements.
Innovation Solution
A movable action lock with a body that has a stop surface to engage or disengage with the bolt carrier, and a cam surface that interacts with a cam on the hammer or trigger to transition between locking and unlocking positions, assisted by a spring bias and manually operable tabs for easy positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pump action mechanism is used to cycle the firearm action, then the rifle provides reliable operation insensitive to ammunition quality, but an effective action locking mechanism must be designed to reliably lock and unlock the bolt carrier
Solution Approach 1:
The action locking mechanism is divided into separate functional components: a lock body with a stop surface for locking the bolt carrier, and a cam surface that interacts with the hammer cam to enable unlocking. This segmentation allows each component to perform its specific function efficiently while maintaining overall reliability without excessive complexity.
Solution Approach 2:
The cam surface on the lock body acts as an intermediary element between the hammer cam and the stop surface. When the hammer pivots, the cam surface translates this motion into movement of the lock body, which then engages or disengages the stop surface with the bolt carrier. This intermediary mechanism ensures reliable locking and unlocking while maintaining simplicity.
2Reliability
If the action lock uses a cam mechanism to transition between locking and unlocking positions, then the bolt carrier can be reliably locked and unlocked, but the mechanism requires precise geometric relationships between components
Solution Approach 1:
The cam surface is designed with specific geometric parameters that change during the hammer's pivot motion. By carefully selecting the cam's radius, position, and shape, the mechanism achieves reliable locking and unlocking without requiring extremely tight manufacturing tolerances on all components. The cam geometry transforms the hammer's rotational motion into the appropriate linear motion of the lock body.
Solution Approach 2:
The cam surface utilizes curved geometry to achieve smooth transition between locking and unlocking states. The curved cam profile ensures continuous contact and controlled motion transfer, reducing the sensitivity to manufacturing variations while maintaining reliable operation. The circular or arc-shaped cam elements provide inherent tolerance compensation.
3Reliability
If a spring is used to bias the action lock into the locking position, then the bolt carrier is reliably locked in battery, but the mechanism requires additional components and space
Solution Approach 1:
The spring-biased mechanism automatically returns the lock body to the locking position (first position) without requiring external intervention. The spring provides continuous biasing force that maintains the locked state, and the cam surface automatically overcomes this bias during hammer pivot to enable unlocking. This self-service mechanism ensures reliable locking while minimizing the need for additional control components.
Solution Approach 2:
The spring provides periodic restoring force that acts on the lock body throughout the cycling operation. The spring is compressed during the unlocking phase and expands during the locking phase, providing automatic return to the locked position. This periodic action ensures consistent reliability while using a simple, space-efficient spring mechanism rather than complex actuation systems.
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
The action lock ensures reliable operation by locking the bolt carrier in battery and unlocking it post-firing, enhancing the rifle's reliability and compliance with regulatory standards, regardless of ammunition quality.
Implementation Method 1
a spring is positioned between the body and a portion of the firearm. The spring biases the action lock into the first position
Implementation Method 2
The cam acts on the cam surface when the hammer pivots from a cocked position to a released position to move the body from the first position to the second position
Data Source
AI summary
An action lock for a Modern Sporting Rifle pump action firearm is pivotably mounted within the lower receiver of the rifle and has a stop surface that engages a contact surface on the bolt carrier when the bolt carrier is in battery. A cam on the hammer or the trigger engages a cam surface on the action lock when the hammer is released by a pull of the trigger. Cam action rotates the action lock out of engagement with the bolt carrier, unlocking it and allowing the fore end grip to be pumped to cycle the action and extract and eject the spent casing and strip and chamber a new round.