20mm M39 Spring Lock Retainer

This 20mm M39 Spring Lock Retainer, identified by FSN 1005-840-1812 and Part Number 8401812, is a specialized military-surplus ordnance component associated with the 20mm M39 aircraft cannon parts family. For collectors of U.S. military aircraft armament parts, Cold War aviation hardware, 20mm cannon components, and stock-numbered government-surplus items, this is a focused support part with strong catalog and reference value.

Public NSN records list the modernized stock number as NSN 1005-00-840-1812, with NIIN 008401812, and identify the item name as Retainer, Spring Lock. The same catalog listing places it under FSG 10 – Weapons and FSC 1005 – Guns through 30mm, confirming its classification as a small ordnance-related component rather than a general hardware item.

The 20mm M39 Aircraft Cannon

The 20mm M39 belongs to the broader family of U.S. Cold War-era aircraft cannon systems. Hill Aerospace Museum describes the M39 series as a U.S.-developed revolver-type aircraft gun, originally known as the T160 during early testing, with more than 35,500 produced for use on aircraft including the F-100, F-101, and other American fighter aircraft.

For collectors, parts connected to the M39 family carry strong historical appeal because they represent the transition from earlier aircraft machine-gun armament into higher-performance 20mm jet-age cannon systems. Small components like this Spring Lock Retainer help preserve the detailed maintenance, parts, and supply-chain side of Cold War aviation armament rather than only the complete cannon or aircraft itself.

The Spring Lock Retainer

The Spring Lock Retainer belongs to the broader family of 20mm aircraft cannon support parts, retainer components, ordnance hardware, and government-stocked replacement parts. Unlike a complete cannon, barrel assembly, receiver, feed system, or ammunition item, this is an individual support component identified by its original-style stock number and part number.

Known catalog information includes:

• Item: 20mm M39 Spring Lock Retainer
• Catalog Nomenclature: Retainer, Spring Lock
• Part Number: 8401812
• Legacy FSN: 1005-840-1812
• Modern NSN Reference: 1005-00-840-1812
• NIIN: 008401812
• Federal Supply Group: 10 – Weapons
• Federal Supply Class: 1005 – Guns through 30mm
• Date Established in Catalog Data: January 1, 1962
• Included Item: Spring lock retainer only

Parts availability records also list P/N 8401812 under NSN 1005-00-840-1812, with descriptions shown as Retainer and Retainer Spring, supporting the part-number match for this small stock-numbered component.

What This Component Supports

As a 20mm M39 Spring Lock Retainer, this item is best understood as a support component for a larger aircraft cannon system. It is not a complete firearm, not a cannon assembly, not a receiver, not a barrel, not ammunition, and not an explosive item.

In practical collecting and display terms, a component like this is especially relevant for:

• 20mm M39 aircraft cannon component collections
• Cold War aviation armament displays
• U.S. military surplus ordnance parts collections
• aircraft gun parts reference displays
• museum exhibits on jet-age fighter armament
• restoration-reference collections where lawful and properly documented
• buyers seeking P/N 8401812 / FSN 1005-840-1812

Because this is a specific part-numbered component, buyers working on a restoration, display, or inventory project should verify fitment against their own technical manuals, illustrated parts breakdowns, equipment records, and applicable legal requirements before purchase.

Historical and Technical Interest

The M39 cannon family is an important part of U.S. aircraft armament history. AirCorps Library identifies an illustrated parts breakdown for the Automatic Gun 20mm M39 and M39A1, listed as T.O. No. 11W1-12-3-14 with a January 30, 1957 revision date, showing the type of technical documentation used to support these aircraft gun systems in service.

Small components like this Spring Lock Retainer help tell the support story behind the larger system. While complete aircraft guns and aircraft displays receive most of the attention, military logistics depended on individual retainers, springs, pins, locks, cams, shafts, covers, and other cataloged parts that allowed complex cannon systems to be documented, stocked, inspected, and maintained through official supply channels.

For collectors and historians, this component is especially relevant to subjects such as:

• 20mm M39 cannon components
• M39 and M39A1 aircraft gun parts
• Cold War U.S. aircraft armament
• FSC 1005 guns-through-30mm components
• jet-age fighter aircraft equipment
• U.S. military maintenance and supply-system history

Public catalog data also lists this NSN with a DMIL Code D entry, meaning buyers should treat it as a controlled surplus component and verify all applicable compliance, transfer, and possession requirements before purchase or use.

About This Spring Lock Retainer

This listing is for one 20mm M39 Spring Lock Retainer, identified as FSN 1005-840-1812 and P/N 8401812.

It is especially well suited for:

• 20mm M39 aircraft cannon parts collectors
• Cold War aviation armament reference collections
• U.S. military surplus component displays
• museum and archival reference use
• aircraft gun technical-parts collections
• ordnance maintenance and supply-system displays
• buyers seeking P/N 8401812 or NSN 1005-00-840-1812

This listing is for the spring lock retainer only unless otherwise stated. No complete cannon, aircraft gun assembly, barrel, receiver, feed mechanism, ammunition, tools, manuals, mounts, or additional accessories are included unless specifically shown or noted.

Why This Spring Lock Retainer Matters

Many military collectibles focus on complete weapons, aircraft, uniforms, helmets, or manuals. This item represents a different but equally important category: the small components that kept complex aircraft armament systems documented, maintained, and supplied.

For collectors, it is a compact and highly specific ordnance component with clear FSN, NSN, and part-number identification. For researchers, it provides a useful example of how small 20mm cannon parts were cataloged within the military supply system. For museums and displays, it helps show the behind-the-scenes hardware that supported the 20mm M39 aircraft cannon family during the Cold War period.

Because this item is identified as a 20mm M39 Spring Lock Retainer with FSN 1005-840-1812 and P/N 8401812, it is a strong fit for anyone building a focused collection of U.S. aircraft armament components, 20mm ordnance parts, or government-surplus cataloged hardware.

Ideal For

This spring lock retainer is a strong fit for:

• 20mm M39 component collections
• M39 and M39A1 aircraft gun reference displays
• Cold War aviation armament collections
• U.S. military surplus ordnance parts collections
• FSC 1005 guns-through-30mm reference collections
• museum and archival display setups
• buyers seeking P/N 8401812 or FSN 1005-840-1812

Approx length .625", Approx width .25", Approx height .25", Approx weight .1lbs.

Pictures are stock images of our inventory. Unless otherwise noted, you will not be receiving the exact item shown in the pictures. The pictures are representative of the item's general condition. The item you receive might be slightly better, or worse, condition than was shown in the pictures.