Stepped Breechblock Housing for Low-Profile Straight-Pull Firearms

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Solution Overview

Problem

Existing hunting and sporting weapons with straight-pull bolt actions have tall, unwieldy breechblock housings due to the coaxial arrangement of the firing pin and firing pin spring, which restrict ease of use and visual appeal.

Innovation Solution

The breechblock is designed with a height-stepped housing and a vertically offset firing pin spring arrangement, allowing the rear part to slide under the buttstock cheek piece, reducing the overall height and relocating the magazine well, while maintaining the firing pin coaxial with the barrel axis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the firing pin spring is arranged coaxially with the firing pin, then the mechanism is simple and reliable, but the breechblock housing becomes tall and unwieldy

Engineering Contradiction:
Improvemechanism reliabilityVSAvoidbreechblock housing height
Core Design Contradiction:
ReliabilityVSLength of moving object

Solution Approach 1:

The patent transitions from a coaxial arrangement (one-dimensional alignment) to an L-shaped offset arrangement, where the firing pin spring is positioned perpendicular to the firing pin axis. This dimensional change allows the spring to be housed in a lower-profile configuration while maintaining its functional integrity and reliability.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent employs an L-shaped curved path for the firing pin mechanism, where the firing pin extends horizontally and the spring extends vertically downward. This curved/geometric reconfiguration allows the mechanism to fit within a compact breechblock housing without requiring excessive height.

Inventive Principle:
Principle #14Spheroidality (Curvature)

2Ease of manufacture

If the bolt housing is made large to accommodate all mechanisms, then all components can be housed, but the weapon becomes heavy and unwieldy

Engineering Contradiction:
Improvecomponent housing capabilityVSAvoidweapon weight
Core Design Contradiction:
Ease of manufactureVSWeight of moving object

Solution Approach 1:

By repositioning the firing pin spring in a perpendicular direction (L-shaped arrangement), the patent eliminates the need for a tall bolt housing. This allows the bolt housing to be compact and lightweight while still accommodating all necessary mechanisms, thereby reducing overall weapon weight.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent segments the breechblock housing into distinct functional zones: the front portion houses the firing pin mechanism, while the rear portion accommodates the offset spring. This segmentation allows for optimized space utilization and reduced material requirements, leading to a lighter overall structure.

Inventive Principle:
Principle #1Segmentation

3Device complexity

If the receiver extends towards the shooter's face, then the mechanism is simple, but it cannot be covered by a cheek rest and creates an unwieldy weapon

Engineering Contradiction:
Improvereceiver structureVSAvoidshooter comfort
Core Design Contradiction:
Device complexityVSEase of operation

Solution Approach 1:

The L-shaped offset arrangement of the firing pin spring allows the receiver to be positioned lower and rearward, away from the shooter's face. This spatial reconfiguration enables the receiver to be covered by the cheek rest, improving shooter comfort and ergonomics without complicating the overall receiver structure.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 design results in a low-profile receiver, minimizing the weapon's overall length, enhancing handling, and protecting the shooter's face from the receiver, while maintaining firing performance and allowing a shorter bolt housing.

Implementation Method 1

a firing pin spring (28), which acts on the firing pin (19), is arranged in a Z-arrangement, i.e., in a vertically offset manner below the longitudinal axis of the firing pin (19)

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP4455602B1Hunting or sporting firearm with compact breechblock
Publication Date: 2026.02.18 DENTLER DANIEL
  • EP4455602B1 patent drawingFigure 1~2
  • EP4455602B1 patent drawingFigure 3~4
  • EP4455602B1 patent drawingFigure 5~6

AI summary

Hunting or sporting firearm with repeating function, in which the ammunition or cartridge is reloaded from a magazine into the chamber in the barrel (1) via a manually operated mechanism, with a bolt (3) which can be operated via a bolt handle (10) and, depending on the actuation, covers the bolt guide or the magazine well of the firearm and locks a bolt head (25) in the barrel (1) or, in the open position, performs a reloading action, wherein the bolt (3) is designed as a stepped breech housing (30) consisting of a higher front part (30a) corresponding to the height of the monoblock (11) or the barrel (1), to which a lower part (30b, 30c) is connected via a recess (31).