The American Cal. .60 Anti-Tank Rifle, T1 & T1E1

Germany, Poland, the UK, and the USSR all developed anti-tank rifles and used them with mixed results (the Germans, in World War I, then all of them, in the early years of World War II) Other nations including Czechoslovakia, Switzerland, Finland and Japan built anti-tank rifles, essentially huge rifles that fired a kinetic penetrator meant to kill tanks. Increasing tank armor during World War II rendered these weapons obsolete rapidly. But most people don’t know that the USA made an effort to develop its own anti-tank rifle — and a strange gun it was!

During World War II, the US Army Air Corps/Air Forces and during Korea the US Air Force, experimented with .60 caliber machine guns — the cartridge was the Cartridge, .60-caliber, T17, and it was developed in 1939 for the T1 and T1E1 Anti-Tank Rifles, a project that hasn’t seen much publicity. It made it as far as test firings in 1942 and 1944. Now all that remains is a few traces of documents that seem no longer to exist in the Springfield Armory archives, and some old photos.

The anti-tank round measured 15.2 x 114mm and was developed no later than 1939. It is a close cousin of the 20 x 102mm cartridge developed for the M39 aircraft cannon (and that would become a decade-plus later the cartridge of the General Electric M61 Vulcan powered-Gatling cannon). Some sources suggest that the 20mm came first, before the 15.2mm (.60) round, but that’s an error. Williams is correct in that the 15.2 came first, and he notes that the round, because of its MG history, is widely available to collectors:

Finally, there is one experimental ATR round which is quite commonly available – the American .60 inch (15.2 x 114). The reason for this is that although the big, gas-operated T1E1 ATR it was designed for was cancelled, the round was adopted for various aircraft MG projects during and after WW2. During this process it was necked down (to make the .50/60) but eventually reached production status when it was necked up to 20 mm to create the 20 x 102 used in the M39 and M61 Vulcan aircraft guns.¹

An official history prepared by the United States Air Force described the .60, in the context of 20mm history, like this:

In 1939 the Army developed a caliber .60 antitank cartridge. Early in World War II our ordnance engineers anticipated a need for a machine gun heavier than our caliber .50 Browning and began work on this caliber .60 which would fire a 1200-grain projectile at the then “hypervelocity” of 3500 fps.

This round was later necked down to caliber .50 and achieved a velocity of 3900 fps! Later yet, it was necked up to 20 mm, known as the 60/20, and fired a 1500-grain projectile at 3300 fps. This round gradually evolved into the M50-series which is now the most widely used 20 mm ammunition in the world.²

It was a powerful round, a little harder-hitting than the excellent Soviet 14.5 x 114mm round used in the Simonov and Degtyaryev anti-tank rifles. It fired an 1180 grain (76.5 g) kinetic penetrator projectile at 3,600 feet per second (1,100 m/s) for a muzzle energy of over 34,000 ft/pounds (46 kilojoules). For comparison’s sake, 7.62 NATO produces about 2,700 ft/lb. (3.6 kJ), and 5.56 about 1300 ft/lb (1.7 kJ). As powerful as it was, if it had been fielded in 1939, it might have been powerful medicine for early-war Axis light tanks, which often had less than 30mm frontal armor.

According to a 1947 ballistics survey, the early rounds (presumably the AT gun ammo) were the Armor-Piercing TS4, BC 2, BC 3, and Tracer BC 3 rounds, and possibly the incendiary T1E6 and HE T19. The rounds that were probably postwar MG rounds (used in guns based on wartime Mauser revolver-cannon designs) included Ball, Incendiary, API and API-T all with T designations.³

But the rifle, which might have been adopted if it were ready with the ammunition in 1939, was not ready for testing until 30 October 1942. By this time its penetration, 32mm at 450m, had been left behind by combat-driven armor development; desultory tests continued, with the weapon being fired once again in June 1944. The gun was ultimately put away without ever being publicized — which is why so many people don’t know the USA had an AT rifle.

The T1 (later T1E1, after an unknown modification) Anti-Tank rifle was a man-portable, gas-operated, tripod-mounted semi-automatic anti-tank rifle designed to be emplaced, displaced and served by a crew of two to three men. The tripod appears to be that used on the M2HB .50 caliber machine gun, and the T1E1 appears to have been about as much a challenge to move and emplace as a .50 can be.

Its design history is lost in time — the only archival material a computer search of Springfield Armory reveals is a single 3/4 view photo — which itself has not been digitized. Apart from some references to the ammunition for its importance in the early development the hugely successful NATO aerial rounds, DTIC is silent on it, and even the familiar backdoor into DTIC through an NTIS search produces only ammunition reports.

The most unusual feature of the T1/T1E1, compared to foreign AT rifles (especially repeating and semi-auto guns), was its feed: the stout .60 rounds were loaded in a Hotchkiss-style tray, which almost certainly makes the T1E1 the last firearm ever designed with this feed. (Japan used several improved Hotchkiss designs to great effect in WWII, but the Japanese weapons were designed earlier). Trays were made to hold five and eight of the .60-cal. rounds. The strange buttstock of the T1E1 was also reminiscent of some early Hotchkiss versions.

The weapon had, in its testing phase, no iron sights and what appears to be a standard rifle telescope.

What became of the test article or articles that was fired in 1942 and 1944 is not known. Scrapping seems highly possible. Had no shaped-charge weapons been available, it might have gone to combat. But the shaped charge was a short-cut to much more terminal effect on enemy tanks than the anti-tank rifle could hope for.

The two photographs shown here, which were scanned from Hoffschmidt but are clearly official US photos, are the only two we have seen of the T1E1. (The Springfield catalog tantalizingly holds out the possibility of a third). It is possible that more documentation exists, uncatalogued, in some museum or other. To our great frustration, what you read in this blog post is just about it.

The T1E1 is remembered now as a dead-end, but an exceedingly powerful one. Other anti-tank rifles tried to get greater velocity with smaller calibers, like the German and Polish 7.92mm guns, or greater power with larger explosive shells, like the many 20mm and a monster Swiss 24mm gun. But in the end, improvements in tank armor on the one hand, and Monroe Effect-based shaped charge weapons on the other, rendered them all obsolete. All of them, and most especially the T1 of which no example is thought to survive,

Notes

1. Williams.
2. Davis, pp. 4-5.
3. Hitchcock, table on p. 29.

Sources:

Davis, Dale M. Historical Development Summary of Automatic Cannon Caliber Ammunition: 20-30 Millimeter. Eglin AFB, FL: Air Force Armament Laboratory, 1984 Retrieved from: Fulltext PDF at: http://www.dtic.mil/dtic/tr/fulltext/u2/a140367.pdf

Hitchcock, H.P. Ammunition Data for Spinning Projectiles. Aberdeen Proving Ground, Maryland: Ballistic Research Laboratory, 1947. May be available at: http://www.dtic.mil/dtic/tr/fulltext/u2/a800469.pdf (or can be accessed through NTIS/NTRL search).

Hoffschmidt, E.J. Know Your Antitank Rifles. Stamford, CT: Blacksmith Corp., 1977.

Rottman, Gordon L. The Book of Gun Trivia: Essential Firepower Facts. New York, 2013: Osprey Publishing.

Williams, Anthony. An Introduction To Anti-Tank Rifle Cartridges. The Cartridge Researcher: The Bulletin of the European Cartridge Research Association, Nov-Dec 2004. Updated version retrieved from: http://www.quarryhs.co.uk/ATRart.htm