AR-15 Sub-Caliber Bolt Assembly Forward Assist Adaptor

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Solution Overview

Problem

AR-15 type firearms experience jamming issues when using sub-caliber ammunition, particularly .22 caliber, due to the bolt not fully closing, which can lead to safety concerns and unreliable firing, especially under dirty conditions or during full automatic firing modes.

Innovation Solution

A sub-caliber action device is developed, featuring a modified bolt assembly and forward assist adaptor that interfaces with the upper receiver's forward assist, incorporating a semi-circular cross-sectional shape with scales for engaging the forward assist pawl and a rear slotted location for anti-bounce functionality, ensuring the bolt remains forward-closed during full automatic firing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a standard bolt assembly is used in AR-15 firearms with sub-caliber ammunition, then the firearm can be operated in various firing modes, but the bolt does not fully close causing jamming issues and unreliable firing

Engineering Contradiction:

Improvebolt closing reliabilityVSAvoidammunition caliber compatibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The bolt assembly is segmented into a standard bolt body and a separate forward assist adaptor component. The adaptor is attached to the forward end of the bolt and provides the missing engagement features needed for sub-caliber ammunition, while the bolt body remains compatible with standard AR-15 operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The forward assist adaptor acts as an intermediary component between the standard bolt assembly and the forward assist mechanism. It provides the necessary engagement surfaces and geometric features that enable the forward assist to properly push the bolt forward, bridging the compatibility gap for sub-caliber ammunition.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the forward assist is struck to ensure bolt closure, then the bolt can be forced into battery, but the extractor component may not be properly clipped around the shell rim

Engineering Contradiction:

Improvebolt closure assuranceVSAvoidextractor engagement reliability

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The forward assist adaptor is designed with pre-configured engagement features that guide the extractor component into proper alignment with the shell rim before the forward assist is actuated. This preliminary positioning ensures that when the bolt is forced forward, the extractor is already correctly clipped around the shell rim.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If the bolt is gently let down to minimize noise, then the closing noise is reduced, but the bolt may not fully close causing potential safety issues

Engineering Contradiction:

Improvenoise reduction capabilityVSAvoidbolt closure completeness

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The forward assist adaptor incorporates self-aligning features that automatically guide the bolt into complete closure regardless of the initial release position. When the charging handle is used to cycle the bolt, the adaptor's geometric features ensure the bolt reaches full battery position without requiring additional manual intervention or risking incomplete closure.

Inventive Principle:

Principle #25Self-service

4Productivity

If the firearm is operated in full automatic mode with sub-caliber ammunition, then continuous firing is possible, but the bolt tends to bounce open during repetitive cycling

Engineering Contradiction:

Improveautomatic firing capabilityVSAvoidbolt position stability

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The forward assist adaptor incorporates features that preemptively counteract the bouncing tendency during automatic firing. The adaptor's engagement geometry with the forward assist mechanism creates a stabilizing effect that prevents the bolt from bouncing open, addressing the problem before it occurs during repetitive cycling.

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS8590199B2Modified bolt assembly with forward assist adaptor for accomodating sub caliber ammunition utilized in an AR-15 type firearm

Publication Date: 2013.11.26 22 EVOLUTION

AI summary

A sub caliber action device installable within an upper receiver of an AR-15 type firearm which interfaces with an upper receiver mounted forward assist for use with such as .22 caliber ammunition. The device includes a generally elongated receiver plate exhibiting a generally lengthwise extending notched interior established between extending sides, with the notched interior seating a bolt and a forward assist adaptor in reciprocating fashion along the receiver plate between an end-most location and a forward secured chamber adaptor. The adaptor is reconfigurable to inertially and linearly displace a limited distance relative to the bolt support sleeve during full auto firing mode and which influences the bolt against the chamber adaptor during striking of the bolt supported firing pin by the hammer.