Polymer Ammunition Primer Insert with Convex Transition
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Solution Overview
Problem
Conventional plastic ammunition cartridges face issues with reliability, safety, and performance due to inconsistent bullet seating, insufficient chamber pressure, and potential casing breakage during firing, which limits their effectiveness and safety in military and sporting applications.
Innovation Solution
A polymeric ammunition cartridge primer insert with a specific design featuring a convex transition region, primer recess, and flash aperture, which enhances the bullet pull force and ensures consistent pressure by providing a secure fit and reliable ignition, addressing the shortcomings of existing plastic cartridges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If conventional plastic cartridge casings are used, then weight is reduced and cost is lowered, but reliability and consistency of bullet seating deteriorate
Solution Approach 1:
The cartridge case uses a composite structure combining polymer material with a metal insert at the base. The polymer provides lightweight properties while the metal insert ensures consistent bullet seating and structural integrity, resolving the contradiction between weight reduction and reliability.
Solution Approach 2:
The metal insert is strategically placed only at the base where it is needed for bullet seating consistency, rather than making the entire case metal. This localized reinforcement maintains lightweight properties while improving reliability at the critical seating interface.
2Ease of manufacture
If conventional plastic cartridge casings are used, then manufacturing cost is reduced, but chamber pressure consistency deteriorates
Solution Approach 1:
The hybrid polymer-metal construction provides the structural rigidity needed for consistent chamber pressure while maintaining the cost advantages of polymer manufacturing. The metal insert ensures uniform pressure distribution during firing.
3Weight of moving object
If conventional plastic cartridge casings are used, then weight is reduced, but resistance to casing breakage during firing deteriorates
Solution Approach 1:
The metal insert reinforces the base area where stresses are concentrated during firing, providing breakage resistance exactly where needed without adding unnecessary weight to the entire cartridge case.
Solution Approach 2:
The combination of polymer and metal materials provides both lightweight properties and enhanced strength at the critical base region, resolving the contradiction between weight reduction and breakage resistance.
Data Source
AI summary
The present invention includes a primer insert for a polymer ammunition cartridge comprising: a top surface; a bottom surface opposite the top surface; a coupling element that extends from the bottom surface, wherein the coupling element comprises an interior surface and an exterior surface, wherein the interior surface comprises: a convex transition region that transitions from the bottom surface to a second segment wherein the transition region has an overall convex shape; a first segment extending from the second segment and terminates at a tip, wherein the first segment has a first segment distance from 0.06 to 0.14 inches and the second segment has a second segment distance from 0.05 to 0.15 inches, wherein the second segment has a second segment angle from +3 to −3 degrees relative to the first segment angle and the first segment has a first segment angle from +6 to −6 degrees from perpendicular to the top surface; a primer recess in the top surface that extends toward the bottom surface; a primer flash aperture positioned in the primer recess through the bottom surface; and a flash aperture groove in the primer recess and positioned around the primer flash aperture and adapted to receive a polymer overmolding through the primer flash aperture.