Lead-Free Rimfire Projectile Design for Cost and Accuracy
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Solution Overview
Problem
Current lead-free rimfire ammunition is either less effective or too expensive to be a viable alternative to conventional lead-based rimfire ammunition, making it impractical in areas where lead is banned.
Innovation Solution
A lead-free projectile designed for rimfire cartridges, made from copper or copper-based alloys with specific geometrical features and manufacturing processes, including a method involving tooling with punches and sintering, to achieve a cost-effective and accurate firing solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free materials are used to replace lead-based projectiles, then environmental harm is reduced, but manufacturing cost increases and effectiveness decreases
Solution Approach 1:
The patent changes the material parameters by using copper and copper-based alloys instead of lead, and modifies the geometrical parameters with specific diameter ratios and depression dimensions to achieve both environmental compliance and cost-effectiveness. The copper alloy formulation (specifically 89-90% copper and 9.5-10% tin) represents a parameter change that maintains performance while eliminating lead.
Solution Approach 2:
The projectile incorporates a depression in the heel portion with specific dimensional relationships (depth 40-135% of nose length, diameter at least 33% of heel diameter) to optimize local properties for rimfire ignition and flight stability. This local geometric modification ensures effective performance with lead-free materials.
2Object-affected harmful factors
If lead-free materials are used to replace lead-based projectiles, then environmental harm is reduced, but effectiveness and accuracy deteriorate
Solution Approach 1:
The patent optimizes geometric parameters including the nose portion length (90-220% of body portion), heel portion length (10-30% of body portion), and diameter relationships to ensure accurate flight and reliable ignition with lead-free copper alloys.
Solution Approach 2:
The depression in the heel portion creates localized properties that enhance rimfire ignition reliability and projectile stability, compensating for the different material characteristics of lead-free alloys.
3Manufacturing precision
If complex geometrical features are added to improve accuracy, then manufacturing complexity increases, but production cost increases
Solution Approach 1:
The depression in the heel portion is a localized geometric feature that provides significant accuracy improvement while occupying minimal space and requiring relatively simple manufacturing processes compared to complex overall projectile redesign.
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 lead-free projectile provides a cost-effective and highly accurate alternative to conventional rimfire ammunition, addressing the need for a affordable and efficient lead-free option in regions where lead is regulated.
Implementation Method 1
moving the lower punch to the second position of the lower punch to compact the powder to form a projectile
Implementation Method 2
sintering the projectile
Data Source
AI summary
A projectile includes a nose portion with a tapered proximal portion and a rounded distal portion, an end of the tapered proximal portion having a first diameter. The projectile has a body portion substantially cylindrical in shape having a second diameter. A first end of the body portion is adjacent to the tapered proximal portion of the nose portion. The projectile has a heel portion substantially cylindrical in shape having a third diameter. A first end of the heel portion is adjacent to a second end of the body portion. The second diameter is greater than the third diameter. The projectile also has a depression defined in a second end of the heel portion. A rimfire ammunition and a method of manufacturing a projectile are also disclosed.