AR Trigger Cam Mechanism for Forced Reset Semiautomatic Fire

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Solution Overview

Problem

Existing semiautomatic firearm trigger mechanisms limit the rate of fire, requiring manual reset after each shot and preventing rapid successive firing without mechanical adaptations that complicate existing firearm platforms.

Innovation Solution

A retrofittable 'drop-in' trigger mechanism for AR-pattern firearms, featuring a three-position safety selector and a cam system that allows for semi-automatic or forced reset semi-automatic operation, enabling rapid firing without manual trigger release.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a standard semiautomatic trigger mechanism is used, then the firearm can be fired single-shot when the trigger is pulled and held, but the rate of fire is limited and manual reset is required after each shot

Engineering Contradiction:

Improverate of fireVSAvoidmanual trigger reset requirement

Core Design Contradiction:

ProductivityVSEase of operation

Solution Approach 1:

The trigger member is preliminarily reset by the cam mechanism during the bolt carrier's rearward movement, preparing the trigger for the next shot before the shooter needs to manually release it. This preliminary action enables faster successive shots by eliminating the manual reset step.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The trigger mechanism performs self-resetting through the cam and follower interaction, where the bolt carrier's movement automatically resets the trigger member without requiring manual intervention. The system serves itself by using the cycling action to prepare for the next shot.

Inventive Principle:

Principle #25Self-service

2Productivity

If devices are used to force reset the trigger with rigid mechanical contact between the trigger member and the bolt, then the rate of semiautomatic fire is increased, but the firearm requires modified fire control mechanism and modified bolt carrier

Engineering Contradiction:

Improverate of semiautomatic fireVSAvoidmodification to firearm platform

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The force reset function is segmented into a separate cam component that interacts with the existing trigger member, rather than modifying the trigger member itself. This allows the reset function to be added without changing the core fire control mechanism or bolt carrier.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The cam acts as an intermediary component between the bolt carrier and the trigger member, transferring the resetting force without requiring direct rigid mechanical contact between the trigger member and the bolt. This intermediary approach maintains compatibility with existing firearm platforms.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If the cam lobe forces the trigger member towards the set position, then rapid firing is enabled, but the trigger member must be precisely positioned to avoid early hammer release

Engineering Contradiction:

Improverapid firing capabilityVSAvoidtrigger member positioning precision

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The cam profile is designed with a gradual approach to the triggering position, cushioning the trigger member's movement before it reaches the set position. This prevents sudden jumps or mispositioning that could cause early hammer release, ensuring reliable operation during rapid firing.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

Enables rapid semiautomatic fire without manual trigger reset, maintaining compatibility with standard M16-pattern bolt carriers and requiring minimal assembly modifications.

Implementation Method 1

the cam lobe does force the trigger member towards the set position

Methodology Applied

Scientific EffectMechanical Force: Mechanical Force

Implementation Method 2

the hammer adapted to be pivoted rearward by rearward movement of a bolt carrier

Methodology Applied

Scientific EffectMechanical Force: Mechanical Force

Data Source

PatentUS12578159B2Firearm trigger mechanism

Publication Date: 2026.03.17 ABC IP LLC

AI summary

A trigger mechanism that can be used in AR-pattern firearms has a hammer, a trigger member, a disconnector, a cam, and a “three position” safety selector having safe, standard semi-automatic, and forced reset semi-automatic positions. In the standard semi-automatic position, rearward movement of the bolt carrier causes rearward pivoting of the hammer and pivoting of the cam from a first position to a second position such that a cam lobe forces the trigger member towards the set position, but prior to reaching the set position the disconnector hook catches the hammer hook, at which time a user must manually release the trigger member to free the hammer from the disconnector to permit the hammer and trigger member to pivot to their set positions so that the user can pull the trigger member to fire the firearm. In the forced reset semi-automatic position, rearward movement of the bolt carrier causes rearward pivoting of the hammer and pivoting of the cam from the first position to the second position such that the cam lobe forces the trigger member to the set position, the safety selector preventing the disconnector hook from catching the hammer hook, at which time the user can pull the trigger member to fire the firearm without manually releasing the trigger member.