Description
WWII U.S. 37mm M51B1 Armor-Piercing Capped Tracer Projectile, 1943 Lot Marking
Item Overview
This original World War II 37mm M51B1 armor-piercing capped tracer projectile was part of the 37×223R ammunition family used by U.S. tank and antitank guns. Its official ammunition classification was Armor-Piercing Capped with Tracer, commonly shortened to APC-T. This listing is for the projectile only; no cartridge case, primer, propellant, weapon, or other components are included.
Identification and Markings
The base is marked “49F,” while the brass rotating band is reported to read “N.P.-LOT-49-1943 - 37MM M1B1.” The lot marking records Lot 49 and a 1943 production date, placing the projectile within the active World War II manufacturing period. The official projectile designation is M51B1; if the band appears to read “M1B1,” the missing “5” may be faint, worn, or obscured. The exact meanings of the “N.P.” abbreviation and “49F” base code have not been established from the available military documentation.
Construction and Features
In its original service configuration, the M51B1 combined a hard steel penetrator body, a softer steel armor-piercing cap, and a lightweight aerodynamic windshield or false ogive. The M51B1 used a pointed armor-piercing cap, while the alternate M51B2 used a cap with a rounded front. The projectile was solid except for a small tracer cavity in the base, which was closed by a metal disk. It contained no explosive bursting charge.
Function and Historical Performance
The M51B1 defeated armor through impact force and penetration. Its armor-piercing cap helped the hardened body engage face-hardened plate without breaking apart, while the windshield improved its flight shape. The original red tracer burned for approximately three seconds, equal to about 2,300 yards of flight. TM 9-1901 lists the M51-series projectile at 6.36" long and records penetration at 1,000 yards and zero-degree obliquity as approximately 2.1" of face-hardened armor or 2.3" of homogeneous armor under period test conditions.
Weapons-System History
M51B1 projectiles were used with the 37mm M3, M3A1, M5, M5A1, and M6 guns. The M3 and M3A1 were towed antitank guns fielded by U.S. forces during the early years of World War II. The related M5, M5A1, and M6 guns armed American tanks and armored vehicles, including light tanks, the turret armament of the M3 medium tank family, and vehicles such as the M8 armored car.
History of Use
The 37mm M51 family was intended for use against light armor and similar material targets. Its capped construction offered better performance against face-hardened armor than the simpler uncapped M74 shot. As heavier wartime tanks became more difficult for 37mm guns to defeat, these weapons remained useful against light vehicles, equipment, firing positions, and other targets that did not require a larger antitank gun. The 1943 marking places this example within that changing period of U.S. armored warfare.
Condition and Safety
This original military-surplus projectile may show oxidation, discoloration, scratches, finish loss, worn markings, rotating-band damage, and other evidence of age or storage. The armor-piercing body has no explosive bursting charge, but the original design included pyrotechnic tracer composition in its base. The tracer-cavity condition of this specimen has been confirmed Empty.
Approx length 6.5", Approx width 1.5", Approx height 1.5", Approx weight lbs.
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