Description
U.S. 20mm M3/M24/Mk 16 Front Recoil-Spring Seat, P/N B7226815, NSN 3120-00-722-6815
Item Overview
This U.S. military surplus component is a front recoil-spring seat for a 20mm automatic cannon. It is identified by part and drawing numbers B7226815 and 7226815. The federal supply system lists it as a Bearing, Sleeve under NSN 3120-00-722-6815. The part is directly identified in the M3 gun technical manual, while its Naval Gun Factory packaging and handwritten “20mm M24 Mk16” marking support an association with related Navy cannon mechanisms. This listing is for one recoil-spring seat only. It does not include a gun, barrel, recoil spring, mount, ammunition, or other parts.
Identification and Specifications
This precision-machined steel component combines the duties of a spring seat and sleeve bearing. Its phosphate finish helps protect the metal during military storage and service.
- Military nomenclature: Seat, Recoil Spring, Front
- Federal designation: Bearing, Sleeve
- Part and drawing numbers: B7226815 and 7226815
- National Stock Number: 3120-00-722-6815
- Federal Supply Class: 3120, unmounted plain bearings
- Confirmed manual application: 20mm Automatic Gun M3
- Supported association: 20mm M24 and Navy Mk 16 cannon family
- Approximate catalog length: 5.505 inches
- Approximate bore: 2.007 inches
- Material: 1045 steel
- Finish: Phosphate
- Item type: Passive mechanical gun component
- Quantity: One recoil-spring seat
Function in the Recoil System
The front recoil-spring seat slides over the gun tube and supports the forward end of the recoil spring. When the cannon fires, the gun tube and front seat move backward and compress the spring. The stored spring force then helps move the recoiling parts forward and return the gun to battery for the next cycle. Its sleeve-shaped body also guides and supports movement around the tube.
Manual Identification
TM 9-229 for the 20mm Automatic Gun M3 identifies this exact component as “Seat, Recoil Spring, Front B7226815” in Figure 85. Figure 86 shows the seat installed around the gun tube as part of the recoil-spring group. Related M24 documentation shows the same general recoil-seat arrangement. Navy records also explain that Mk 16 guns were made by modifying M3 and M24 mechanisms, which supports the Navy application written on the original packaging.
History of the M3 Automatic Gun
The 20mm M3 was developed from the wartime T31 program and belonged to the American family of cannons based on the Hispano-Suiza 404 design. It became a standardized U.S. weapon near the end of World War II. The M3 was a percussion-fired, rear-seared automatic cannon that used gas pressure to unlock the action, with blowback force helping complete the operating cycle. Its rate of fire was generally listed at about 700 to 750 rounds per minute.
M24 and Mk 16 Development
The M24 was developed as an electrically fired version of the same basic 20mm cannon design and became substitute standard in 1947. The U.S. Navy later created the Mk 16 family by modifying existing M3 and M24 guns. Important Navy changes included different feed equipment and a recoil-operated chamber lubricator that reduced the need to lubricate ammunition by hand. Because several models and modifications existed, this part should not be treated as universally interchangeable without checking the correct parts manual.
History of Use
M3 and M24 cannons served in American aircraft during the closing years of World War II and the early Cold War. Modified Mk 16 guns later served with the Navy, including use on small patrol and riverine craft. Navy 20mm cannons provided rapid fire against surface targets, shoreline positions, and other close-range threats. Their service with small combat boats during the Vietnam era continued the working life of a mechanism first developed for aircraft use.
Naval Gun Factory Connection
The package bears a Naval Gun Factory label and the handwritten notation “20mm M24 Mk16.” The Naval Gun Factory operated at the Washington Navy Yard and manufactured, modified, and supported naval weapons. These markings add useful supply-history context and are consistent with Navy handling of M24 and Mk 16 parts. They do not, by themselves, prove compatibility with every Mk 16 modification.
Compatibility Notice
Part number B7226815 is directly confirmed for the M3 cannon by TM 9-229. Its use with an M24 or Mk 16 is supported by the shared design history, recoil arrangement, and package markings, but the exact gun model and modification should be checked before installation. Buyers should compare the part number, dimensions, drawing revision, and illustrated parts breakdown for their specific equipment.
Collector and Research Value
This part is a useful example of the internal recoil system used in an important American 20mm cannon family. It is well suited for museum displays, technical study, restoration reference, and collections focused on military aviation, naval weapons, or the Naval Gun Factory. The marked packaging may offer added value to collectors interested in military supply history.
Condition
This vintage military surplus part may show storage grease, dried preservative, finish wear, scratches, discoloration, surface marks, or other signs of age and handling. Packaging style, markings, and condition may vary.
Ideal For
This specialized cannon component is suitable for historical collections, institutional research, and properly documented restoration projects.
- 20mm M3 automatic-cannon displays
- M24 and Mk 16 weapons research
- Naval Gun Factory collections
- Military aviation and naval exhibits
- Ordnance restoration references
- Museum and archival collections
Approx length 5.505", Approx width 2.5", Approx height 2.5", Approx weight 1.1 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.
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