A mini-history of Project Vulcan and its off-shoots
Near the end of the Second World War, the US Army Air Force (pre-U.S.A.F.) and the US Army Ordnance Department started work on high cyclic rate weapons for aircraft use. Given the introduction of jet propulsion, engagement times would be severely limited; thus, more projectiles would need to be fired in order to achieve hits. Cleves “Doc” Howell suggested to Melvin M. Johnson, Jr. that attaching an external motor to a multi-barreled Gatling gun might achieve the high cyclic rates desired. Dr. Richard J. Gatling had played with such an idea in the 1890s, and patented it in 1893. Reportedly, Gatling’s motorized design was capable of 1,500 to 3,000 rpm. However, there was no perceived need for it at the time.
With permission from Colonel René R. Studler, Johnson was allowed to experiment with antique Gatlings in the Aberdeen Proving Grounds’ Ordnance Museum. He was finally allowed to convert an 1886-vintage Gatling in .45-70 that had 10 barrels and a 103 round drum. For safety sake, black-powder ammunition loaded to original specs was used for the tests, but in spite of this, Johnson was able to achieve cyclic rates of 4,000 rpm and 5,500 rpm. Impressed with Johnson’s report, Ordnance awarded General Electric a contract to develop a modern belt-fed model in June 1946. The goal was a five barrel, .60 caliber (15mm) design, with a minimum cyclic rate of 1,000 rpm per barrel. The design was later changed to include six barrels.
In 1949, the prototype T45 was ready. It achieved 2,500 rpm, which was increased to 4,000 rpm by 1950. By 1952, GE had three different models: the .60 caliber T45, the 27mm T150, and the 20mm T171. After trials at Springfield Armory, the T45 and T150 were dropped from consideration, leaving the T171. In 1956, the T171E3 was officially adopted as the M61. In the same year, the 30mm T212 was introduced. (The T212 fired a less powerful 30mm cartridge than that used in the 1970s vintage GAU-8A “Avenger” developed for the A10 Thunderbolt – a/k/a the Warthog.) The rotary design was eventually scaled up for cartridges as large as 37mm in the T250 used by the prototype Vigilante Anti-Aircraft System.
Interest in the development of a 7.62mm NATO version began in 1957. GE initiated an independent research and development project in 1960, and had the basic design of the Minigun ready by 1962. At this time, the USAF awarded a contract for further development. The M134 (later designated the GAU-2/A by the USAF) was designed for use in aircraft gun pods such as the SUU-11/A; however, GE did not receive any significant orders until US involvement in the Vietnam War increased. Once the M134 was proven successful in gunship conversions of the C47, CH47, and UH1, it was only a matter of time before ground applications were envisioned for the M134.
Admittedly, the M134 were meant for mounted use and were never intended to be hand-held. Stembridge Gun Rentals, which provided firearms for film productions from 1916 to 1999, modified at least two real M134 for use in films such as Predator and Terminator 2. The cyclic rate was reduced to 1700 rpm in order to reduce torque and to lower the voltage required to power the motor that rotates the barrels. When Stembridge quit the gun rental business due to the oppressive legal climate in California, their set of modified M134 were placed up for sale. For $125,000, a qualified individual could buy one, including the associated movie props, spare parts, and live barrels. (For blank cartridge use, the Stembridge M134 was equipped with constricted barrels for the purpose of enhancing the muzzle flash.) For additional money, Stembridge’s Minigun wrangler Dan Sprague would provide instruction on its use and maintenance.
Note: Some folks are convinced that the Minigun in Predator is the M134’s little brother: the 5.56x45mm XM214 “Six Pak.” However, the XM214’s barrels offer a far more tapered profile when assembled. In addition, the XM214 can be distinguished by its use of only two barrel clamps.
by Daniel E. Watters, Small Arms Historian
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Last Revised: 09/29/2008
This article was originally published at The Gun Zone — The Gunperson’s Authoritative Internet Information Resource. My friend and mentor Dean Speir has graciously hosted my articles at TGZ for nearly 16 years. These articles would likely have never appeared online without his constant encouragement and assistance.
With TGZ’s closure in early 2017, Dean encouraged me to find a new home for my scholarship so it wouldn’t be lost in the dustbin of the Internet. Loose Rounds has welcomed me with open arms. In the future, I intend to expand my legacy TGZ articles and add new contributions here at Loose Rounds.