Editing M61 Vulcan (section)

==Development==
At the end of [[World War II]], the [[United States Army Air Forces]] began to consider new directions for future [[military aircraft]] guns. The higher speeds of [[jet engine|jet-powered]] [[fighter aircraft]] meant that achieving an effective number of hits would be extremely difficult without a much higher volume of fire. While captured German designs (principally the [[Mauser MG 213|Mauser MG 213C]]) showed the potential of the single-barrel [[revolver cannon]], the practical rate of fire of such a design was still limited by ammunition feed and barrel wear concerns. The Army wanted something better, combining an extremely high rate of fire with exceptional reliability.<ref name="archive.org">https://archive.org/stream/The_Machine_Gun_V5/The_Machine_Gun_V5_djvu.txt M61 Al, CHAG, and GAU-8/A Machine Guns, History of Vulcan</ref> 

In 1947, the [[United States Air Force|Air Force]] became a separate branch of the military. The new Air Force made a request for a new aircraft gun. A lesson of World War II air combat was that German, Italian, and Japanese fighters could attack American aircraft from long range with their cannon main armament. American fighters with [[M2 Browning#AN.2FM2|.50&nbsp;caliber (12.7&nbsp;mm)]] main armament, such as the [[North American P-51 Mustang|P-51]] and [[Republic P-47 Thunderbolt|P-47]], had to be close to enemy aircraft in order to hit and damage them. The [[Hispano-Suiza HS.404|{{cvt|20|mm|in}} Hispano cannon]] carried by the [[Lockheed P-38 Lightning|P-38]] and [[Northrop P-61 Black Widow|P-61]], while formidable against propeller-driven planes, had a relatively low rate of fire in the age of jets, while other cannons were notoriously unreliable.

In response to this requirement, the Armament Division of General Electric resurrected an old idea: the multi-barrel [[Gatling gun]]. The original Gatling gun had fallen out of favor because of the need for an external power source to rotate the barrel assembly, but the new generation of turbojet-powered fighters offered sufficient [[electric power]] to operate the gun, and electric operation was more reliable than [[gas-operated reloading]].<ref name="img294.imageshack.us">{{Cite web |type= image |format= JPEG |place= US |publisher= Image shack |url= http://img294.imageshack.us/img294/2433/eleckeygatling.jpg |title= Elec key Gatling |access-date= 5 September 2010 |archive-url= https://web.archive.org/web/20110725152641/http://img294.imageshack.us/img294/2433/eleckeygatling.jpg |archive-date= 25 July 2011 |url-status=dead }}</ref> 

With multiple barrels, the rate of fire per barrel could be lower than a single-barrel revolver cannon while providing a greater overall rate of fire. The idea of powering a Gatling gun from an external electric power source was not a novel idea at the end of World War II, as [[Richard Jordan Gatling]] himself had done just that with a patent he filed in 1893.<ref>[https://web.archive.org/web/20110725152641/http://img294.imageshack.us/img294/2433/eleckeygatling.jpg Archived copy of US Patent #502,185 by R.J. Gatling, for an electric-powered Gatling-gun]</ref> 

During [[World War I]], a similar 12-barreled [[Fokker-Leimberger]] aircraft rotary machine gun, powered by either the aircraft engine or an electric motor, had been under development by the [[German Empire]].{{Citation needed|date=May 2023}}

In 1946, the Army issued General Electric a contract for "Project Vulcan", a six-barrel weapon capable of firing 7,200 rounds per minute (rpm).<ref>{{Cite web |title= The Gatling Gun |access-date=2008-09-28 |url= http://tri.army.mil/lc/cs/csa/aagatlin.htm#M61 |date=5 October 2005 |archive-url= https://web.archive.org/web/20080921095536/http://tri.army.mil/LC/CS/csa/aagatlin.htm |archive-date =2008-09-21 |publisher= Aircraft Armament & Small Arms Product Support Integration Directorate |first1= Paul F |last1= Wahl |first2= Donald R |last2= Toppel |orig-year= Arco Publishing Company, New York, NY, 1965}}</ref> Although European designers were moving towards heavier {{cvt|30|mm|in|3}} weapons for better hitting power, the U.S. initially concentrated on a powerful {{convert |0.60|in|mm|adj= on}} cartridge designed for a pre-war anti-tank rifle, expecting that the cartridge's high [[muzzle velocity]] would be beneficial for improving hit ratios on high-speed targets.<ref name="archive.org"/> The first GE prototypes of the {{convert|0.60|in|mm|adj=on}} caliber T45 were ground-fired in 1949; it achieved 2,500&nbsp;rpm, which was increased to 4,000&nbsp;rpm by 1950. By the early 1950s, the USAF decided that high velocity alone might not be sufficient to ensure target destruction and tested {{cvt|20|and|27|mm|in|sigfig=3}} alternatives based on the {{convert|0.60|in|mm|adj=on}} caliber cartridge. These variants of the T45 were known as the T171 and T150 respectively and were first tested in 1952. Eventually, the standard 20×102&nbsp;mm cartridge was determined to have the desired balance of projectile/explosive mass and muzzle velocity, resulting in an optimum balance of range, accuracy and [[Kinetic energy penetrator|kinetic energy]] on target.<ref>{{Cite web|url=https://www.dau.mil/cop/ammo/DAU%20Sponsored%20Documents/PEO%20Ammo%20Portfolio%20Book%202017.pdf|title=PEO Ammunition Systems|website=dau.mil|archive-url=https://web.archive.org/web/20181106171753/https://www.dau.mil/cop/ammo/DAU%20Sponsored%20Documents/PEO%20Ammo%20Portfolio%20Book%202017.pdf|archive-date=6 November 2018|url-status=live}}</ref>

The development of the [[Lockheed F-104 Starfighter]] revealed that the T171 Vulcan (later redesignated ''M61'') suffered problems with its [[Belt (firearms)|linked ammunition]], being prone to misfeed and presenting a [[foreign object damage]] hazard with discarded links. A linkless ammunition feed system was developed for the upgraded ''M61A1'', which subsequently became the standard cannon armament of U.S. fighters.<ref name ="f_106_delta_dart_m61">{{cite web|url=https://www.f-106deltadart.com/weapons_20mm_cannon.htm|title=M61A1 GAU 4 20-MM Vulcan Cannon|access-date=12 July 2017|archive-url=https://web.archive.org/web/20161125131351/http://www.f-106deltadart.com/weapons_20mm_cannon.htm|archive-date=25 November 2016|url-status=live}}</ref>

In 1993, [[General Electric]] sold its aerospace division, including GE Armament Systems along with the design and production tooling for the M61 and GE's other rotary cannon, to [[Martin Marietta]]. After Martin's merger with [[Lockheed Corporation|Lockheed]], the rotary cannon became the responsibility of Lockheed Martin Armament Systems. Lockheed Martin Armament Systems was later acquired by [[General Dynamics]], which produces the M61 and its variants {{asof|2000|lc=y}}.<ref name= "fas_m61">{{cite web |url= http://www.fas.org/man/dod-101/sys/ac/equip/m61.htm |title= M61 20mm cannon |access-date= 2009-02-28 |date= 23 April 2000 |publisher= [[Federation of American Scientists]] |archive-url= https://web.archive.org/web/20011214122616/http://www.fas.org/man/dod-101/sys/ac/equip/m61.htm |archive-date= 14 December 2001 |url-status= live }}</ref>