Cartridge Case Base Piece Cold Forming for Precise Extractor Grooves

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Solution Overview

Problem

Existing methods for manufacturing extractor grooves in multi-part cartridge cases are suboptimal for cost-effective mass production, leading to manufacturing tolerances and holding force issues, and often result in surface defects that impair the extraction function.

Innovation Solution

The method involves forming the extractor groove on the base piece of a multi-part cartridge case through cold forming before creating the receptacle for the case shell, using tools that minimize radial material displacement to ensure higher strength and precision, allowing for simpler and less expensive tooling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If machining is used to manufacture the extractor groove, then manufacturing precision can be achieved, but manufacturing cost and complexity increase

Engineering Contradiction:

Improveextractor groove precisionVSAvoidmanufacturing cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent replaces traditional machining operations with a cold-forming process using a punch-die tool assembly. The extractor groove is formed by plastic deformation of the base piece material through the punch tool, eliminating the need for subtractive machining operations. This substitution maintains dimensional accuracy while significantly reducing manufacturing cost and complexity for mass production.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of manufacture

If segmented punch-die tools are used to form the extractor groove, then manufacturing cost decreases, but surface defects are created that impair extraction function

Engineering Contradiction:

Improvemanufacturing costVSAvoidextraction function

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The punch tool is designed as a segmented assembly with multiple independently movable segments that can flex during the forming operation. This segmentation allows the tool to conform to the workpiece geometry without creating sharp edges or surface defects, while still enabling cost-effective manufacturing through simplified tool construction and ease of maintenance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent modifies the geometric parameters of the extractor groove during the forming process by controlling the punch profile and deformation characteristics. The groove dimensions, including depth, width, and curvature radius, are optimized to ensure proper engagement with the firearm extractor while maintaining a smooth surface finish that prevents defects.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If the extractor groove is formed after the receptacle, then tooling complexity increases, but manufacturing flexibility is improved

Engineering Contradiction:

Improvetooling complexityVSAvoidmanufacturing flexibility

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The extractor groove is formed in the base piece before the receptacle for the case shell is created. This preliminary action allows the groove geometry to be established and optimized independently, enabling better control over extraction function. The subsequent receptacle forming operation can then focus solely on creating the case housing feature without interference from groove formation requirements.

Inventive Principle:

Principle #10Preliminary action

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

This approach enhances the holding force between the base piece and case shell, ensures higher dimensional accuracy of the extractor groove, and prevents surface defects, making the manufacturing process more cost-effective and suitable for automated mass production.

Implementation Method 1

forming the extractor groove on the base piece of a multi-part cartridge case through cold forming before creating the receptacle for the case shell

Methodology Applied

Scientific EffectCold forming: Cold-forming

Implementation Method 2

forming the extractor groove on the base piece of a multi-part cartridge case through cold forming

Methodology Applied

Scientific EffectPlastic deformation: Plasticity

Data Source

PatentEP4405634B1Method for producing a base piece of a multi-part cartridge case

Publication Date: 2026.04.01 RUAG AMMOTEC AG

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AI summary

The present invention relates to a method for producing a base piece for receiving an ignition cap for a multi-part cartridge case, in which method an extraction groove for engagement therein by a firearm ejector is produced by shaping, before a receptacle for a case sleeve of the multi-part cartridge case for receiving a projectile is in particular produced by shaping. The present invention also relates to a tool arrangement for producing a base piece, to a base piece and to a cartridge case.