Complete your U.S. aircraft cannon restoration with this specialized internal component. This 20mm M39 Operating Slide Cam Insert is an original military-pattern part for the M39-series 20mm revolver cannon, identified by Part Number 8401915 and NSN 1005-00-840-1915.

The M39 was one of the most important American aircraft cannons of the Cold War era. Developed from postwar revolver-cannon concepts and standardized in the 1950s, the M39 family became a well-known 20mm weapon system used in U.S. combat aircraft such as the F-86, F-100, F-101, B-57, and later the F-5. Its compact revolver design gave American aircraft a hard-hitting internal cannon at a time when aircraft armament was rapidly shifting from machine guns to more powerful automatic cannon systems.

This Operating Slide Cam Insert belongs to the internal operating system of the M39 family. As the nomenclature suggests, it is part of the operating slide / cam assembly, one of the precision-fit component groups that helps govern the motion and interaction of the cannon’s internal moving parts. On a restoration, these smaller internal pieces matter just as much as the larger visible assemblies. A major component may make the gun look complete, but correct detail parts like this are what preserve its true mechanical identity.

That is what makes this item especially desirable. It is not a generic spacer, bushing, or hardware piece. It is a specifically identified M39-series operating-slide component, tied directly to the internal mechanism of one of the most recognizable U.S. aircraft cannons of the 1950s and 1960s.

For collectors, restorers, and museums, parts like this are valuable because they were rarely saved once separated from the gun. Large assemblies tend to survive. Internal components—especially inserts, cams, plungers, retainers, and latch pieces—were more likely to be lost, mixed with other parts, or discarded entirely. That makes correctly identified original M39 internals especially appealing today.

This part is a strong fit for:

M39, M39A1, M39A2, and related M39-series cannon restorations
U.S. aircraft armament collections
Museum and educational displays focused on Cold War aircraft gun systems
Technical reference collections of original U.S. ordnance parts
Spare parts inventories for advanced restoration work

If you are building out a historically accurate 20mm M39 cannon project, assembling a reference set of original aircraft cannon internals, or simply putting away difficult-to-source parts while they are still available, this Operating Slide Cam Insert is exactly the kind of original detail component worth having on hand.

Ideal For

This part is an excellent fit for:

20mm M39-series cannon restorations
U.S. aircraft armament collections
Museum and educational displays
Technical parts-reference collections
Spare-parts inventories for original Cold War cannon systems

Approx length 3", Approx width 2.5", Approx height 1", Approx weight 2lbs.

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.

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