Half-cock trigger safety assembly

Patent No. US10330413 (titled "Half-cock trigger safety assembly") on Aug 11, 2017. The application was issued on Jun 25, 2019.

’413 is related to the field of firearm trigger mechanisms, specifically focusing on safety systems designed to prevent accidental discharge. In traditional firearms, a “half-cock” or safety notch is often used to catch a falling hammer if the primary sear fails. However, these systems typically rely on the primary sear surface to impact the safety notch, which can degrade the precision-ground finish of the sear over time and negatively impact the consistency and feel of the trigger pull.

The underlying idea behind ’413 is to isolate the critical sear surfaces from impact or friction when the firearm enters a safety or partially-cocked state. By designing the geometry so that the primary sear surface is suspended within a safety recess without touching the hammer, the invention ensures that accidental drops or mechanical slips do not mar the surfaces responsible for a crisp trigger break. This preserves the mechanical integrity of the trigger’s feel even after the safety mechanism has been engaged.

The claims of ’413 focus on a hammer and trigger geometry where the hammer rotates through a significant angular distance—at least half of its total travel to the firing pin—before reaching a stable safety position. In this position, the primary sear surface is explicitly free of engagement with the hammer. Instead, the assembly utilizes secondary surfaces, specifically a trigger release barrier and a hammer safety engagement surface, to arrest the hammer's motion and prevent the trigger from being pulled to release it.

In practice, the system functions by providing a dedicated notch in the hammer that acts as a clearance zone for the trigger sear. When the hammer slips from full-cock, the trigger’s forward end moves upward into this notch. Rather than the sear catching the hammer, a separate trigger release barrier surface meets a corresponding hammer barrier. This secondary interface is engineered to be transverse to the hammer's rotation, effectively locking the mechanism and requiring the hammer to be manually recocked to reset the system.

This approach differs from prior art by prioritizing the longevity of the sear surface finish. While traditional 1911-style half-cock notches use the sear as a mechanical stop, this invention treats the sear as a sensitive component to be protected. By shifting the mechanical load of a safety catch to secondary barrier surfaces and ensuring the safety position occurs late in the hammer's swing, the design provides a robust drop-safe mechanism that does not sacrifice the high-performance characteristics of a single-stage trigger.

How does this patent fit in bigger picture?

Technical Landscape

In the mid-2010s when ’413 was filed, firearm trigger mechanisms were typically implemented using sear-based engagement systems where a primary trigger sear surface directly interfaced with a hammer notch to maintain a cocked state. At a time when safety mechanisms commonly relied on secondary notches located in close proximity to the primary sear surface, such as traditional half-cock notches, hardware constraints made it non-trivial to prevent surface degradation of the primary sear during accidental hammer drops. Systems of this era generally required the primary sear to catch the hammer at a shallow angular distance from the cocked position, which often resulted in the high-precision sear surfaces impacting the hammer and altering the mechanical feel or weight of the trigger pull over time.

Prosecution Position

The disclosed invention represents a technical advancement through an architectural shift in the spatial relationship between safety engagement surfaces and primary sear surfaces. By configuring the trigger assembly such that the hammer rotates a significant angular distance—at least half the distance to the firing pin—before reaching a stable safety position, the system enables a geometry where the primary trigger sear surface remains entirely free of engagement with the hammer during a safety catch event. This integration of a dedicated trigger release barrier surface and a hammer release barrier surface, distinct from the primary sear surfaces, overcomes the technical constraint of sear surface wear. The resulting capability ensures that the integrity and friction profile of the primary sear are preserved even if the safety mechanism is engaged, maintaining consistent trigger pull characteristics while providing a robust mechanical stop against unintentional discharge.

Claims

The patent contains a total of 20 claims, with claims 1, 13, and 19 serving as the independent claims. These independent claims focus on the mechanical configuration of a firearm trigger and hammer assembly, specifically defining a safety or partially-cocked position where the hammer is rotated a significant distance from the cocked position and the trigger sear is disengaged from the hammer sear. The dependent claims serve to further specify the geometric relationships of the components, such as angular rotation percentages, the inclusion of barrier surfaces to prevent accidental release, the use of specific recesses, and the application of these features within single-stage trigger systems.

Key Claim Terms New

Definitions of key terms used in the patent claims.

Term (Source)	Support for Specification	Interpretation
First angular distance (Claim 1)	The angular distance between the stable/static cocked position and the stable/static safety position can be at least half, preferably at least 60%, or more preferably at least 70% of the angular distance between the stable/static cocked position and the stable/static uncocked position. In some instances, the angular distance between the stable/static cocked position and the stable/static safety position is at least 30° or preferably at least 40°.	The specific degree of hammer rotation between the cocked position and the safety position, defined as being at least 50% of the total rotation required to strike the firing pin.
Hammer release barrier surface (Claim 13)	A trigger release barrier surface can be arranged to engage a hammer release barrier surface to prevent movement of the trigger from releasing the hammer. It is also provided that the hammer release barrier surface can be tangential to an imaginary circle concentric with a hammer axis of rotation about which the hammer rotates.	A structural surface on the hammer that engages the trigger release barrier surface to halt hammer rotation and trigger travel during a safety event.
Single-stage trigger and hammer assembly (Claim 19)	In single stage triggers, the trigger sear surface disengages from the hammer sear surface when a sufficient force has been applied to the trigger to overcome the friction between the trigger sear surface and hammer sear surface. The trigger assembly and/or components thereof may be of a single stage trigger assembly. The present disclosure provides trigger assemblies that preserve the integrity of the trigger sear surface when the trigger assembly enters a “half-cocked”, safety configuration.	A trigger mechanism where the hammer is released by overcoming sear friction in a single continuous motion, modified here to include a safety position that protects the sear surfaces.
Stable safety position (Claim 1)	The present disclosure provides trigger assemblies that preserve the integrity of the trigger sear surface when the trigger assembly enters a “half-cocked”, safety configuration. In the stable safety position the trigger sear surface is free of engagement with the hammer. This prevents the trigger sear surface from becoming rougher or smoother, which would impact the force or feeling of the trigger pull.	A state where the hammer is partially rotated from its cocked position but prevented from reaching the firing pin, characterized by the trigger sear surface being completely disengaged from the hammer to prevent wear on the sear.
Static cocked position (Claim 19)	In single stage triggers, the trigger sear surface disengages from the hammer sear surface when a sufficient force has been applied to the trigger to overcome the friction between the trigger sear surface and hammer sear surface. When the hammer is in the static cocked position the trigger sear surface engages the hammer sear surface. The hammer is rotatable from a static cocked position to a static safety position.	The initial ready-to-fire state of a single-stage trigger assembly where the primary trigger sear and hammer sear are fully engaged and under tension.
Trigger release barrier surface (Claim 13)	A trigger release barrier surface can be arranged to engage a hammer release barrier surface to prevent movement of the trigger from releasing the hammer, when the assembly is in the stable/static safety position. In some arrangements, the hammer/trigger release barrier surface is transverse to the hammer/trigger safety engagement surface. The trigger safety engagement surface is transverse to the trigger sear surface.	A specific physical interface on the trigger, distinct from the sear surface, designed to block trigger movement by contacting a corresponding hammer surface when the assembly is in a safety state.

Litigation Cases New

US Latest litigation cases involving this patent.

Case Number	Filing Date	Title
4:25-cv-00299	Jun 6, 2025	Abc Ip, Llc V. Harrison Gunworks Llc

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US10330413

Application Number: US15674932A
Filing Date: Aug 11, 2017
Publication Date: Jun 25, 2019
External Links: Slate, USPTO , Google Patents

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