Description
75mm M309A1 High-Explosive Round with Fired Projectile and M557 PDSQ Fuze
Item Overview
This 75mm M309A1 high-explosive round combines a fired M309A1 projectile, an inert M557 point-detonating superquick nose fuze, and an M31A1 perforated cartridge case. The case has no primer. All components are inert and contain no explosive filling, propellant, igniter, live primer, detonator, booster, or other energetic material. The round is assembled for collecting, study, museum display, or restoration and cannot be fired.
Identification and Features
The M309A1 belonged to the 75×408mmR ammunition family developed for the U.S. M20 recoilless rifle and its T21E12 developmental counterpart. The original fixed cartridge joined a steel high-explosive projectile to a perforated M31A1 case. This example uses a fired projectile, so its rotating band may show rifling marks from its passage through a barrel. The projectile, fuze, and case are assembled as an inert display piece and are not represented as an original factory-matched cartridge.
- Model: M309A1
- Caliber: 75mm
- Ammunition family: 75×408mmR recoilless rifle
- Original service type: High explosive, blast and fragmentation
- Projectile condition: Fired and inert
- Nose fuze: Inert M557 PDSQ
- Cartridge case: M31A1 perforated case
- Primer: Not present
- Primary weapon: 75mm Recoilless Rifle M20
- Original complete-round length: Approximately 28.92 inches
- Original loaded service weight: Approximately 22.57 pounds
- Status: Completely inert and for display only
Fired Projectile and M31A1 Case
The M309A1 projectile had a relatively thin steel body, a boat-tailed base, an internally threaded nose, two bourrelets, and an integral pre-engraved rotating band. On this fired example, the rotating band may carry visible impressions from the barrel’s rifling. The M31A1 case was made with hundreds of perforations and originally used internal liners to hold the propellant before firing. During discharge, gas passed through the case openings and escaped through the weapon’s rear venturi to reduce recoil. This display case contains no propellant, and its primer opening is empty.
Original Service Function
A live M309A1 cartridge carried approximately 7.43 pounds of TNT and was intended to produce blast and fragmentation against troops, field positions, light structures, and exposed or lightly protected equipment. Army data lists an original projectile weight of approximately 14.40 pounds, a muzzle velocity near 990 feet per second, and a maximum range of about 6,580 yards. These figures describe the original loaded service cartridge only. This offered round has been made permanently inert and contains none of the materials required for firing or functioning.
M557 PDSQ Nose Fuze
The M557 was a point-detonating impact fuze with superquick and delay functions for use with high-explosive artillery and recoilless-rifle ammunition. Superquick action caused a live projectile to function close to the point of impact, while the delay option allowed limited penetration before detonation. Early M309A1 technical illustrations commonly show the M51A5 fuze, while later Army ammunition guidance includes the M557 among the impact fuzes used with 75mm high-explosive ammunition. The M557 fitted to this display is inert and nonfunctional.
M20 Recoilless Rifle System
The U.S. Army developed the 75mm M20 recoilless rifle during World War II to give infantry units a portable weapon with more power and range than smaller shoulder-fired launchers. Production began in 1945. The approximately 103-pound weapon could be mounted on an M1917A1 machine-gun tripod or installed on vehicles such as jeeps. Its vented breech allowed part of the propellant gas to escape rearward, balancing much of the recoil and eliminating the heavy recoil system required by conventional artillery. The result was a crew-served support weapon that could be moved and positioned more easily than a standard 75mm gun.
Historical Service
The M20 saw limited service near the end of World War II and much wider use during the Korean War. Its shaped-charge ammunition was first used against armored vehicles, but the weapon became especially useful for close infantry support after proving less effective against newer tanks. High-explosive ammunition such as the M309A1 was suited to enemy troops, bunkers, trenches, buildings, and other field positions. American and allied forces continued using the M20 family during the early Cold War, and related weapons appeared in several later conflicts before newer recoilless rifles and guided missiles took their place.
Condition
This is an inert surplus display round assembled with a fired projectile, an inert M557 PDSQ fuze, and an M31A1 case without a primer. The fired projectile may show engraved rifling marks, impact marks, dents, pitting, oxidation, finish loss, discoloration, or other evidence of firing and recovery. The case and fuze may also show scratches, corrosion, storage wear, tool marks, faded markings, or finish differences. Component markings and minor construction details may vary between examples. No weapon, ammunition container, tools, or additional accessories are included. Please check the pictures for the general condition of the item.
Ideal For
This M309A1 display round represents an important part of American recoilless-rifle development and makes a substantial addition to collections covering infantry support weapons, historic ammunition, and twentieth-century U.S. military equipment.
- M20 recoilless rifle displays
- 75mm ammunition collections
- World War II collections
- Korean War exhibits
- Inert fuze and projectile collections
- Military museums and educational displays
- Recoilless weapon development exhibits
Approx length 29", Approx width 5", Approx height 5", Approx weight 18lbs.
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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