Description
U.S. 20mm T1 Experimental Inert Round — German 20×138mmB Pattern, 1941
Item Overview
This is an extremely scarce complete U.S. 20mm T1 experimental inert round from 1941. It includes both the cartridge case and its fitted 20mm projectile. The T1 was an American copy of the German 20×138mmB cartridge, commonly known as the Long Solothurn. Its experimental designation, early production date, and foreign-pattern design make it a significant example of American World War II ordnance development. Very few of the US manufactured 20mm T1 rounds are still in existence. This is the only one available, so you will be receiving the one in the photos.
Identification and Features
The T1 designation identifies an experimental U.S. cartridge rather than standardized service ammunition. Its long, bottlenecked, belted case follows the basic form of the German 20×138mmB cartridge.
- U.S. experimental designation: 20mm T1
- Date: 1941
- Configuration: Complete inert round with case and projectile
- Parent cartridge pattern: German 20×138mmB
- Common parent-cartridge name: Long Solothurn
- Case style: Bottlenecked and belted
- Caliber: 20mm
- Case length: Approximately 138mm
Construction and Function
A complete 20mm round combines the projectile and cartridge case into one ammunition unit. In a live round, the case would hold the primer and propellant while the projectile would be seated in the case mouth. When fired, the case would expand against the chamber walls to seal the propellant gases. The raised belt near the base provided a controlled seating surface within a weapon chamber. This example has been rendered completely inert for collection and display.
Documented End-Item Applications
The U.S. T1 copied the cartridge pattern used by several European automatic cannon and heavy anti-tank weapons. Documented 20×138mmB applications included the German 2 cm FlaK 30, FlaK 38, FlaKvierling 38, and KwK 30 and KwK 38 vehicle guns. The same cartridge family was also used by Solothurn S-18/1000-series anti-tank rifles, the Italian Breda Model 35 cannon, and the Finnish Lahti L-39 anti-tank rifle.
T1 Development History
The 20mm T1 was produced during the rapid expansion of American ordnance research in 1941. U.S. engineers studied foreign cannon, cartridges, and manufacturing methods as the nation prepared for possible entry into World War II. Copying the German 20×138mmB design allowed American ordnance personnel to evaluate an established high-velocity 20mm cartridge. The T1 remained an experimental design and was not adopted as standard U.S. service ammunition.
Parent-Cartridge History
The 20×138mmB cartridge was developed during the early 1930s through arms work associated with Rheinmetall and its Swiss affiliate, Waffenfabrik Solothurn. The letter B identifies its belted case. Its greater case capacity produced the velocity needed for antiaircraft fire, ground support, and early anti-armor work. The cartridge became one of the best-known European 20mm cannon rounds of World War II.
Parent-Equipment History
The German 2 cm FlaK 30 entered naval service in 1930 and Luftwaffe service in 1935. It was followed by the faster-firing FlaK 38 and the four-barrel FlaKvierling 38. These recoil-operated cannon normally used detachable 20-round magazines. They could fire high-explosive, tracer, armor-piercing, and practice ammunition against air and ground targets.
Larger Weapon-System Background
Weapons chambered for the 20×138mmB parent cartridge ranged from large anti-tank rifles to automatic cannon on towed, fixed, vehicle, and naval mounts. Light antiaircraft units used these weapons to defend troops, airfields, supply areas, vehicles, and ships from low-flying aircraft. Their high rate of fire also made them useful against lightly armored vehicles, firing positions, and exposed troops.
History of Use
The parent 20×138mmB cartridge family saw extensive combat during World War II. German forces used it in light antiaircraft cannon across Europe, North Africa, and the Eastern Front. Italian, Finnish, Swiss, and other forces also used weapons chambered for this cartridge family. The American T1 belongs to the experimental side of this history and documents U.S. study of a major foreign cannon cartridge during 1941.
Condition
This listing includes one complete inert 20mm T1 display round with its cartridge case and projectile. It contains no live primer, propellant, explosive filler, or functioning pyrotechnic material. It is intended only for historical collection, research, and display.
Ideal For
This experimental round fits collections focused on American ordnance development, foreign-ammunition evaluation, and World War II automatic cannon systems.
- U.S. experimental-ammunition collections
- World War II ordnance displays
- 20mm cannon-ammunition collections
- Long Solothurn cartridge displays
- Military museums and educational exhibits
- Historic cartridge and projectile research
Approx length 8.5", Approx width 1", Approx height 1", Approx weight 0.6lbs.
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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