Barrel Extension Interface: Index Pin Diameter 0.154" ±0.0005"

Component Specifications

Definition

The Barrel Extension Interface is a critical mechanical component in firearm receivers that provides the mounting surface and alignment features for attaching barrel extensions. It ensures precise concentric alignment between the barrel extension and receiver, maintains headspace control, and transfers firing forces from the barrel assembly to the receiver structure. This interface typically includes threaded connections, indexing pins, and mating surfaces that must maintain tight tolerances for reliable firearm function.

Working Principle

The interface operates on mechanical attachment principles, using precision threads and alignment features to create a rigid connection between the barrel extension and receiver. It maintains proper headspace by controlling the distance between the bolt face and chamber, while transferring recoil forces through the receiver structure. The design ensures repeatable alignment during barrel changes or maintenance.

Materials

4140 or 4150 chromoly steel, heat-treated to RC 28-32; Alternative: 8620 steel case-hardened; Surface treatment: Nitride or phosphate coating for corrosion resistance

Technical Parameters

Parameter	Typical range	Notes & selection driver
Hardness	RC 28-32 core, RC 60+ surface for nitride
Thread Pitch	1.0625-16 UNEF or metric equivalent
Surface Finish	32 Ra or better on mating surfaces
Thread Engagement	Minimum 1.5 times diameter
Index Pin Diameter	0.154" ±0.0005"
Squareness To Bore	0.0005" per inch maximum
Concentricity Tolerance	0.001" TIR maximum

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

SAE J429, MIL-S-5000

Engineering Analysis

Risks & Mitigation

Improper installation leading to headspace issues
Thread damage from cross-threading
Material fatigue from repeated disassembly
Corrosion in mating surfaces

FMEA Triads

Trigger: Incorrect torque application during installation
Failure: Thread stripping or improper headspace
Mitigation: Use calibrated torque wrenches and follow manufacturer specifications precisely

Trigger: Contamination in thread engagement area
Failure: False torque readings and improper seating
Mitigation: Thorough cleaning before assembly and use of appropriate lubricants

Trigger: Material defects or improper heat treatment
Failure: Cracking or deformation under firing stresses
Mitigation: Material certification and non-destructive testing of critical components

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

±0.0005" on critical dimensions, 0.001" TIR concentricity

Test Method

CMM verification, thread gauge inspection, headspace gauge testing, proof load testing

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

Check the legal entity, factory address, ownership, certifications, and direct contacts.

CNFX does not score or rank suppliers. Buyers must verify all claims and documents with the legal manufacturer before ordering.

Manufacturers of Barrel Extension Interface

Manufacturer profiles associated with Barrel Extension Interface.

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Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review

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Frequently Asked Questions

What is the primary function of a barrel extension interface?

The primary function is to provide a precise and secure mounting point for barrel extensions on firearm receivers, ensuring proper alignment, headspace control, and force transfer during firing.

Can barrel extension interfaces be interchanged between different firearm models?

No, they are typically model-specific due to variations in thread patterns, dimensions, and indexing systems. Always use manufacturer-specified interfaces for your firearm model.

What maintenance is required for barrel extension interfaces?

Regular inspection for thread wear, cleaning of mating surfaces, and verification of torque specifications during reassembly. Avoid overtightening which can damage threads.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Barrel Extension Interface