Polymer Ammunition Primer Insert with Convex Transition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional plastic ammunition cartridges face issues with reliability, safety, and performance due to inconsistent bullet seating, insufficient chamber pressure, and structural integrity, leading to potential weapon jams or damage.
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 structural integrity by providing a consistent interlock between the primer insert and the middle body component, ensuring reliable firing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If plastic cartridge casings are used to reduce weight and cost, then weight and manufacturing cost decrease, but reliability and structural integrity deteriorate
Solution Approach 1:
The patent employs a composite structure combining polymer material for the cartridge body with a metal primer insert. This hybrid approach maintains the weight reduction benefits of plastic while introducing a metal component specifically at the primer interface to ensure structural integrity, consistent interlock, and reliable firing performance that pure plastic cannot achieve
Solution Approach 2:
The invention applies local quality enhancement by introducing a metal primer insert only at the critical primer recess area rather than making the entire cartridge metal. This localized reinforcement provides the necessary strength and consistency at the firing interface while keeping the rest of the cartridge lightweight and cost-effective
2Ease of manufacture
If conventional plastic primer inserts are used, then manufacturing cost decreases, but bullet pull consistency and chamber pressure deteriorate
Solution Approach 1:
The metal primer insert provides superior dimensional stability and consistency compared to plastic, ensuring uniform bullet pull force and consistent chamber pressure generation. The metal material maintains precise geometric tolerances during manufacturing and firing, addressing the precision deficiencies of conventional plastic inserts
Solution Approach 2:
The convex transition region with its curved geometry provides optimized stress distribution and consistent contact surfaces for bullet seating. The curved profile ensures uniform pressure application during firing, improving bullet pull consistency while maintaining manufacturability
3Weight of moving object
If plastic cartridge casings are used, then weight decreases, but structural integrity and safety deteriorate
Solution Approach 1:
The hybrid polymer-metal construction combines the lightweight advantages of plastic with the structural strength of metal at critical load-bearing interfaces. The metal primer insert specifically reinforces the headspace and firing pin interface areas, ensuring adequate strength for safe firing while maintaining overall cartridge weight reduction
Solution Approach 2:
Local reinforcement with metal material at the primer insert provides the necessary structural integrity at the most critical stress points during firing, while the rest of the cartridge body remains lightweight plastic. This targeted approach ensures safety without the penalty of full-metal construction
4Ease of manufacture
If conventional plastic primer inserts are used, then manufacturing cost decreases, but interlock consistency and firing reliability deteriorate
Solution Approach 1:
The metal primer insert provides superior and consistent interlocking with the polymer overmolding compared to plastic-on-plastic interfaces. The metal substrate ensures reliable mechanical engagement and consistent primer seating, thereby improving firing reliability while maintaining cost-effectiveness through selective material usage
Data Source
AI summary
The present invention provides 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.