Two-Stage Cartridge Case Neck for Reduced Projectile Tension

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Solution Overview

Problem

Existing ammunition cartridge designs face challenges in achieving optimal retention force, shelf-life, durability, and ballistic performance, particularly in high-strength materials like steel, which often require crimping and can compromise surface integrity.

Innovation Solution

A two-stage neck design for the cartridge case featuring an interference band and a clearance band, providing varying diameters and lengths to achieve interference and clearance retention forces without crimping, enhancing retention force and reducing manufacturing complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If high-strength materials like steel are used for cartridge cases, then durability and corrosion resistance are improved, but retention force and surface integrity are compromised

Engineering Contradiction:

ImprovedurabilityVSAvoidretention force

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The neck region is selectively modified with a two-stage design featuring an interference band and clearance band, creating localized geometric variations that optimize retention force without compromising the overall strength and corrosion resistance of the high-strength steel cartridge case

Inventive Principle:

Principle #3Local quality

2Strength

If high-strength materials like steel are used for cartridge cases, then durability and corrosion resistance are improved, but surface integrity is compromised

Engineering Contradiction:

ImprovedurabilityVSAvoidsurface integrity

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The two-stage neck design with interference and clearance bands creates localized geometric features that achieve proper projectile retention without requiring crimping operations that would damage the surface integrity of the high-strength steel case

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If traditional single-stage neck design is used, then manufacturing is simpler, but retention force is insufficient

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidretention force

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The neck is divided into two distinct stages: an interference band portion and a clearance band portion. This segmentation allows each region to perform its specific function (retention and clearance respectively) while maintaining compatibility with standardized manufacturing processes

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The neck diameter is varied along its length with two distinct diameter regions. The interference band has a smaller diameter to create retention force, while the clearance band has a larger diameter to provide clearance, achieving optimal retention without complex manufacturing

Inventive Principle:

Principle #35Parameter changes

4Reliability

If crimping is used to increase retention force, then retention force is improved, but manufacturing complexity and surface damage increase

Engineering Contradiction:

Improveretention forceVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The retention function is achieved through localized geometric features (interference band) rather than through a crimping process, eliminating the need for complex crimping equipment and operations while maintaining high retention force

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The mechanical crimping action is replaced by a geometric interference fit design. The interference band's reduced diameter creates friction and normal forces that retain the projectile without requiring external crimping forces or equipment

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 two-stage neck design offers improved retention force comparable to brass, increased durability, and reduced susceptibility to corrosion, while maintaining compatibility with standardized dimensions and simplifying manufacturing processes.

Implementation Method 1

The interior of the two-stage neck comprises an interference band that is adjacent the second end of the body and comprises an interference diameter extending an interference length along the two-stage neck, the interference band configured to provide an interference fit with the projectile resulting in an interference retention force

Methodology Applied

Scientific EffectInterference fit: Friction

Implementation Method 2

The interior of the two-stage neck also comprising a clearance band comprising a clearance diameter and extending a clearance length along the two-stage neck, the clearance diameter being greater than the interference diameter, the clearance band configured to provide an interference fit with the projectile resulting in a clearance retention force

Methodology Applied

Scientific EffectClearance fit: Friction

Data Source

PatentUS20250314467A1Reduced tension cartridge case with two-stage neck

Publication Date: 2025.10.09 FEDERAL CARTRIDGE CO

AI summary

Devices and methods for reducing tension force on a projectile by a neck of a cartridge case. A two-stage neck has a clearance band and an interference band, the clearance band providing a reduced retention force on the projectile relative to the interference band.