Description
20mm M39 Spring Operating Guide, P/N 8401755
The 20mm M39 Spring Operating Guide, P/N 8401755 is a rod-form internal component associated with the operating-spring system of the M39 20mm automatic aircraft gun. The guide’s head is visibly stamped 8401755 B.
This component supported and aligned an operating spring within the gun’s mechanism. It is the spring guide only, not an operating spring, complete spring group, or complete M39 gun.
Historical Significance
The M39 began under the T160 designation and became a standard U.S. Air Force 20mm automatic gun during the post-World War II jet era. Period Air Force documentation describes it as a gas-operated, belt-fed, electrically fired aircraft weapon.
The M39’s rapid operating cycle placed repeated loads on its internal moving parts and springs. Guides such as the 20mm M39 Spring Operating Guide, P/N 8401755 helped keep the spring system aligned within that larger mechanism.
What This Item Is and Does
The 20mm M39 Spring Operating Guide, P/N 8401755 has a long guide shaft and a shaped, slotted head. The shaft provided a straight support path for an operating spring as the spring compressed and returned during the gun’s mechanical cycle.
Its function was limited to guiding and supporting the operating spring. The guide did not feed ammunition, fire a cartridge, or perform the complete operating cycle by itself.
Key Features
- Component type: Spring Operating Guide
- Supplied part number: 8401755
- Visible head marking: 8401755 B
- Associated weapon: M39 20mm automatic aircraft gun
- Rod-form guide with a shaped, slotted head
- Designed as part of the gun’s operating-spring system
- Single loose component; operating spring and complete gun are not included
- Visible surface oxidation, handling wear, discoloration, and residue
Why This Item Matters
This marked guide represents a specific internal component from the M39 aircraft-gun system. Its form helps illustrate how a high-rate automatic weapon used separate guides and springs to control the movement of its operating mechanism.
The visible part marking makes it useful as a collection reference, restoration-pattern example, or display component for studying U.S. postwar aircraft armament.
About This Item
The photographed 20mm M39 Spring Operating Guide, P/N 8401755 has the marking 8401755 B stamped around its head. The component has a long rounded shaft with a broader slotted head at one end.
The photographed example shows widespread surface oxidation, dark discoloration, handling wear, and residue across the shaft and head.
Ideal For
This identified M39 component is well suited for:
- M39 20mm aircraft-gun component collections
- U.S. military aviation and aircraft-armament displays
- Museum reference collections
- M39 operating-system restoration reference
- Research into postwar automatic aircraft-gun mechanisms
- Technical education, film, and prop departments
Approx length 8", Approx width 1.5", Approx height 1", Approx weight .5lbs.
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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