Description
U.S. M39-Series 20mm Aircraft-Cannon Feeder Idler Sprocket, P/N 8401428, NSN 1005-00-305-0731
Item Overview
This military-surplus idler sprocket is associated with the ammunition feeder used on the M39 series of 20mm aircraft cannons. Its five-lobed shape and keyed center match the layout of sprockets shown in period U.S. Air Force M39 feeder illustrations. This listing is for the idler sprocket only. It does not include a cannon, feeder assembly, ammunition chute, rammer, shaft, links, cartridges, or aircraft components.
Identification Details
The part number and National Stock Number provide the main identification points for this specialized aircraft-armament component. Buyers should confirm both numbers before ordering because fit may differ among M39 gun and feeder variants.
- Official nomenclature: Sprocket, Idler
- Part number: 8401428
- National Stock Number: 1005-00-305-0731
- Federal Supply Class: 1005, Guns through 30mm
- Associated system: M39-series 20mm aircraft cannon
- Ammunition family: Linked 20×102mm cartridges
- Notable features: Five-lobed profile and keyed center
- Country of origin: United States
- Item included: One idler sprocket
Role in the M39 Feeder
The M39 used a disintegrating-link feeder to move linked 20×102mm ammunition into position for loading. Feeder sprockets engaged and guided the belt as the feeder shaft turned with the gun’s drum system. The rammer then pushed each cartridge out of its link and into a drum chamber, while the empty link continued through the feeder and was discharged separately. This idler sprocket helped support that controlled belt path. Its keyed center was made to engage a matching shaft and keep the sprocket correctly positioned.
M39 Weapon-System History
The M39 began as the experimental T160 and became a standard U.S. Air Force aircraft cannon during the early 1950s. It was a gas-operated, belt-fed, electrically fired revolver cannon with one barrel and a five-chamber rotating drum. A period Air Force manual listed a firing rate of about 1,500 rounds per minute. The weapon could be arranged for left- or right-hand feeding by changing and relocating certain parts. Later versions included the M39A1, M39A2, and M39A3.
History of Use
The T160 was tested in combat on modified F-86F-2 Sabres during the Korean War before the system entered wider service as the M39. M39-series cannons later armed aircraft such as the F-86H Sabre, F-100 Super Sabre, F-101A and F-101C Voodoo, B-57B Canberra, and several F-5 Freedom Fighter and Tiger II models. M39-armed F-100s and B-57Bs served in Southeast Asia, where their cannons supported air combat, close air support, and ground-attack missions. The M61 Vulcan replaced the M39 in many later U.S. designs, but the M39A2 remained closely linked with the long-serving F-5 family.
Collector and Restoration Value
P/N 8401428 is a specialized piece of Cold War aircraft-armament history. Its unusual five-lobed form makes it useful for M39 feeder displays, museum research, cutaway exhibits, and properly documented restoration projects. It also offers collectors a close look at the mechanical system that moved linked ammunition through one of the U.S. Air Force’s best-known early jet cannon designs.
Condition
This military-surplus component may show finish wear, scratches, grease, surface oxidation, discoloration, tool marks, identification markings, or other signs of service and long-term storage. Condition and markings may vary between available pieces.
Ideal For
This idler sprocket is well suited for collections, displays, research, and restoration projects involving American aircraft armament.
- M39 aircraft-cannon collections
- F-86H, F-100, F-101, B-57B, and F-5 research
- Cold War aviation displays
- Aircraft feeder-mechanism exhibits
- Museum and archival collections
- Military surplus parts collections
Approx length 2.5", Approx width 2.5", Approx height 0.5", Approx weight 0.2 lbs.
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.
Please visit our page about order lead times here: Order Lead Times.