Springfield Armory Museum - Collection Record

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Maker/Manufacturer:GENERAL ELECTRIC
Date of Manufacture:1963
Eminent Figure:
Catalog Number:SPAR 5630
Measurements:OL: 31 1/2" BL: 22" 35 lbs.

Object Description:

Manufactured by General Electric, Burlington, Vt. in 1963 - Standard XM134 machine gun. Six barrels chambered for 7.62mm NATO. Gatling type system. 4-groove rifling; right hand twist. Dependent on external source of power. Utilizes a 3 horsepower electric motor for driving power. Fed by 4,000 round link belt. Muzzle velocity 2,850 fps. Rate of fire approximately 6,000 rpm. Weapon has an overall length of 31 1/2", the barrels measure 22" and weighs approximately 35 lbs. empty. No bolts in gun. Several pins missing. Tag ties installed for temporary fix.

Plate: GENERAL GE logo ELECTRIC/GUN XM134 B3E10733 XM134/SER NO. 5831311/AF08 (835) 3484/BURLINGTON, VT. MADE IN USA/NP 210459
Side: 63E10972/REV-P.

Weapon transferred to the Museum on 22 August 1966. At that time weapon was appraised at $30,000.

1JUL63 - 30JUN64 - "Gun, Machine, 7.62mm, XM133/XM134 - The start of this fiscal year found the Armory continuing to furnish engineering services to General Electric and Elgin Air Force Base.
During the First Quarter, General Electric, under an Air Force Contract, had function fired a prototype model weapon to over 35,000 rds. Sixty per cent of component parts for ten guns had been fabricated. The Armory continued to furnish barrels for assembly to GE weapons. Plans for installing the XM133/XM134 in helicopters was initiated.
In the Second Quarter of FY64 and at the request of Hqs, USAWC, the Armory initiated a Determination and Finding for the purpose of entering into a contract with General Electric for the follow-on development of the XM134 M.G. and the fabrication of 15-20 weapons. In addition, it was decided, by higher authority, to negotiate a contract with GE for a high rate of fire machine gun to fire .223 and XM144 ammunition. It was also planned to negotiate a contract with GE for a twin high rate gun system for the UH-1B to be known as the XM15 Armament System.
Third Quarter FY64 activities showed a marked increase. The D/F referred to in previous paragraph was approved on 19 March 1964 and the Armory moved out to consummate a contract with General Electric on continuing the development of the XM134 and the furnishing of (20) weapons.
An engineering test unit (XM134), that was delivered to the Eglin Air Force Base in the Second Quarter of FY64, fired 80,000 rds. Performance was far in excess of what had been expected from this weapon.
In order to support the XM133/134 weapons that had been turned over to the Army, Springfield Armory placed a contract with General Electric for repair parts to support these weapons.
R&E sources were sought for the XM15 Subsystems by synopsizing in the U.S. Commerce Business Daily.
Several meetings were held in April 64 to discuss design problems of the XM133 gas drive, weapon system as well as the development status of the XM134 electric drive weapon system. Also, during April, General Electric submitted its proposal for continuing the development of the XM134 and the furnishing of specific hardware under an Army contract. G.E.'s proposal was on the basis of a FF type of contract.
Negotiations began on the G.E. contract, at BPD, on 6 May 1964. GE was requested to submit a proposal based on a FF type of contract. The proposal submitted was at a cost of $966,000 which was considerably higher than had been anticipated.
An in-process review meeting was held at Hqs., USAWC on 2 June 64 to discuss the technical characteristics of the XM15 Armament Subsystem.
During June, negotiations continued on the proposed Army contract for the XM134 and discussions centered around a CPIF type of contract. Incentives on overall cost and performance were received and agreed upon....
During this period, the General Electric Co. continued to work on the development and design of a lightweight gun pod, complete with a 7.62mm high rate of fire gun, an ammunition feed and storage system, and a self-contained power source for the gun and feed system operation. Prime emphasis was To insure scheduled delivery, a General Electric-Air Force decision was made to utilize the electrical drive configuration for the engineering test unit pods that were delivered in late October 1963. Unit #1 was fired for approximately 105,000 rounds with results surpassing all General Electric and Air Force expectations. In late April 1964, an Air Force decision was made to take delivery of all nine pods with electric drive. This was done to insure scheduled delivery. No gas drive units were delivered to the Air Force because of the marginal performance of the gas drive and spring starter.
Army designations given to the items developed under the Air Force contract are as follows:
1. Machine Gun, 7.62mm: Gas Drive, XM133
2. Machine Gun, 7.62mm: Electric Drive, XM134
3. Armament Pod, Aircraft, 7.62mm Machine Gun: High Rate XM18
The following hardware was delivered to the Army (Springfield Armory): two XM18's, two XM133's, and three XM134's. Springfield Armory supplied 7.62mm barrels during the contract period.
Spare components for the Army gun and pods and two ballasted drop pods were purchased from the General Electric Co.
Army contracts for follow-on development of the XM134 and engineering support services were let to General Electric. All effort to be expended under these contracts will occur in FY65."
1JUL64-30JUN65 - "On 30 June 64, a follow-on development contract (Contract DA-19-020-AMC-00410 (Y) on the XM134 MG was entered into between AMC and General Electric. It was a CPIF contract with provisions for incentives on overall costs and performance. Target cost was $833,000 plus a total target fee of $71,600. The contract included the delivery of eighteen (18) XM134 MG's and Repair Parts and Feeders. The guns were generally destined to be used in the development and testing of new aircraft armament subsystems. Also on 30 June 64, Contact DA-19-020-AMC-0433 (Y) for $69,160 was signed by General Electric and the Boston Procurement District for engineering support services of the XM133/XM134 MG's, XM18 Pod and YAT 37 nose installation. A meeting was held at Springfield Armory, on 6 Aug 64, to discuss the XM134 development and support services contracts, technical problems, additional gun requirements, redesign of firing pin, redesign of barrel clamp, Springfield Armory's XM134 MG drawing requirements, etc. On 25 Aug 64, a meeting was held with General Electric engineers to discuss the relative merits of 22 and 20 volt drive motors for the XM134 MG on the XM21 Subsystem.
During September 1964, the Armory fired two (2) XM133 weapons. One fired 1100 rds. with one malfunction. This was a failure to start and was caused by marginal, spring-starter, energy. The second gun stopped at 70 rounds. The cause for this stoppage was not definitely determined. A rotor in one of the weapons was damaged.
At the request of the Army, General Electric furnished a quotation on six (6) XM134 MG's. Delivery quoted was two (2) in 2.5 months and four (4) in 3.5 months. A contract for these guns was consummated in October 1964.
In October, Springfield Armory reviewed and approved test instructions to be used by General Electric in the performance evaluation of the XM134 MG. Test included interchangeability, endurance and environmental tests. The test plan was put into effect in November 1964.
Further testing of the XM133 MG at the Armory, in October 1964 resulted in a stoppage similar to that occurring in September 1964. The gun fired out of an unlocked position and caused damage to the bolt and motor. Also occurring in October 1964 was the submission by General Electric of proposed design changes to eighteen (18) MG's to be fabricated under Contract DA-19-020-AMC-00410Y.
The function firing of the first four (4) XM134's MG's (Serial number 101, 102, 103 and 104), fabricated under DIn November 1964 a contract for the additional six (6) XM134 MG's was signed with General Electric. These guns were required for use in the XM21 Subsystem development program.
In December 1964, one of the two (2) endurance guns, referred to in a previous paragraph, was fired 99,000 rounds at a rate of 3000 spm. There was a barrel failure at 72,000 rounds. There were some misfires. No parts, except barrels, were replaced. With respect to the 6000 spm endurance gun, it was found necessary to incorporate a clearing mechanism in the feeder portion of the weapon.
Also in December 1964, General Electric submitted to Springfield Armory a rough draft of the results of its studies under a Value Engineering program. Some of the changes recommended by General Electric required further investigation and possibly some trial runs.
In order to meet an urgent need of the Air Force, sixty XM133 gun barrels were modified by Springfield Armory, to XM134 gun barrels. Twelve (12) XM134 barrels and a quantity of repair were shipped from General Electric to the Air Force on 8 January 1965.
In January 1965, the fabrication of XM134 Barrels, as GFE to General Electric, was accelerated to 100 per month beginning March 1965. In the Barrel design improvement area, Springfield Armory's Test Branch started the test firing of newly designed 'heavy weight' barrels.
Early in January 1965, SA received $453,000 in R&E funds for support of the XM134 MG program. Scope of activity included continued development of the gun, the furnishing of technical information and supply for XM134 spare parts, the furnishing of data in support of the XM21 Subsystem program, continued engineering development of the XM133 MG, fabrication of barrels of the XM133 and XM134 MGs, and technical support and support hardware for conduct of the XM134 ET/ST.
Early in February '65, SA received $100,000 out of a total of $490,000 APE funds requested. Of the amount received, $25,000 was transferred to Quality Assurance as a portion of their requirement of $195,000 for TDP preparation.
Endurance firing of the 6000 spm, XM134MG was completed at G.E. in February '65. During the last 9000 rounds, of the 100,000 fired, there was no malfunction whatsoever. However, in comparing the performance o of the 6000 spm gin with the 3000 spm gun, it was found that the 3000 spm gun was superior.
The transfer of funds to the extent of $139,000 from the R&D portion of the XM134 program for the purpose of supporting the XM23/XM24 Armament Subsystem program, was requested of by SA Hq AWC. The Command was advised by SA that the withdrawal of these funds would prevent the planned accomplishment of the following programs:
a. Contractor development to assure the attainment of a 25,000 round reliability factor.
b. Fabrication of four (4) XM134MG's for additional development/improvement testing and the proving of proposed value engineering design changes.
c. Investigation/studies of the current XM134 Barrel and the fabrication/test of experimental barrels.
Eighteen 'heavy' design of the XM134 Barrels were completed by the Operations Division in March '65 and an endurance test of said barrel on 30 March 65. Environmental testing, on the weapon itself continued at G.E. during March.
On 11-12 March '65, a design review meeting was held at SA with representatives of G.E. and Hq. AWC. Discussions involved thThe testing of the 'heavy' barrel for endurance continued on into April '65. It performed very satisfactorily. A drawing on the new design was sent to Hq. AWC on 14 April '65.
On 12 April '65, SA requested Hq. AWC to revise an APE funding request, submitted on 1 Sept. '64, from $100,000 to $415,000 for 'in-house' effort and from $390,000 to $75,000 for 'out-house' effort. The main reason for this change was to expedite the delivery of a TDP required in December '65.
Finalized in April '65 was a POMM on the XM134MG. Also finalized were reports on endurance and environmental testing at G.E. A new activity in April '65 was the placing of a contract, with G.E., for a quality assurance study on the XM134.
In the early part of May, SA received $390,000 in APE funds. This was in addition to the $100,000 previously furnished and this completed the original request for $490,000.
During the 4th Qtr. of FY65, R&E conducted low and high temperature environmental tests on the XM134 MG. At -65 F the gun would not fire because of feed problems. Although there were several stoppages when the guns were subjected to operating temperatures of - 25 F, - 50 F and +155 F, they were not attributed to the environment because like stoppages had previously occurred at ambient temperatures.
A meeting held at Hq. AWC on 8-9 June '65 was very beneficial in resolving exceptions that G.E. had requested consideration on before finalizing the contract on the XM18 Pod procurement contract. A number of exceptions cited by G.E. were with respect to the XM134 MG."
1JUL65 - 30JUN66 - "On request from higher authority, OD personnel furnished technical assistance to two contractors (Thompson-Ramo-Woolridge and Harrington & Richardson Arms) on fabrication of the XM-134 7.62mm Barrel (the "Mini" barrel), several hundred of which were made at the Armory in FY 1965. Late in FY 1966, the Armory was asked to make a quantity of these barrels but because of phase-out conditions, limited manpower, and the lead time needed to procure material, this order had to be declined....
Technical support was provided by representatives from the engineering and test areas to tests of the XM134 and the XM21 subsystem at APG, Edwards AFB, and Yuma Proving Ground.
Thirty-six special barrels (with partial liners) were fabricated. These will be tested in an erosion and endurance test program to determine the effect of the partial barrel liner.
Technical assistance was provided the General Electric Co. on the development of the XM133 gas drive.
A program was initiated to investigate flash suppressors (program was prompted by XM28 requirement) for the XM134 gun. Two types were designed and fabricated, one a modified M14 flash suppresser, the other a can-type blast diffuser. Both devices were put through several firing tests, with photographs taken on flash, some blast pressures were recorded and shock wave diagrams were plotted. Additional testing will be required before a final design-type selection can be made.
As a result of the preliminary reports from the XM134/XM21 service test, an investigation was conducted to determine a means to eliminate the ammunition-discarding feature of the delinking feeder during its clearing cycle. Effort was expended toward redesigning the delinking feeder to provide a declutching device.
A program to design a cycle counter for the XM134 was initiated. Final design, detailing, preparation of drawings, and prototype fabrication were completed. Preliminary testing of the XM21, at the Yuma Proving Ground appeared successful. Further development testing will be requested....
The XM134 Value Engineering Study, performed by a contractor under the supervision of Springfield Armory in 1964, was reported for the first time in the fourth quarter of 1966. Initial savings of approximately $210,000 were reported for the 82 guns. The cost of this study was approximately $20,000. It is expected that significant savings will be realized in future years1JUL66 - 30JUN67 - "Representatives from the engineering and test areas provided technical support to tests of the XM134 and XM21 at APG.
The erosion and endurance test firing of the special barrels (with partial stellite liners) was started near the end of the 3rd quarter. Due to lack of priority on this program, testing has been and continues to be periodically delayed by higher priority testing programs. Firing of this test program will continue to depend on priorities, workload, and manpower availability. One set of these partially-lined barrels were test fired at Elgin AFB as part of the Air Force Part Life Test Program. The barrels were removed from testing after 20,2389 rounds because of high extraction forces. The barrels are currently being examined at the Armory.
A representative visited Hq, AWC to provide technical support for the firing of a pintle-mounted XM134 with the night vision devices, using modified barrels with modified M14 flash suppressors. Required amount of flash suppression was apparently attained to allow effective use of one or two of the night vision devices.
The design of the 'clamp on' flash suppresser which requires no modification to existing hardware was completed. Eight prototype 'clamp-on' flash suppressors were fabricated and successfully pull-tested. These flash suppressors are currently being test fired to check adequacy of design. Review of the present design of the declutching device for the delinking feeder was completed. Review has shown that additional design effort could result in greater utilization of existing components thereby enhancing retrofit of field units. Continuation of development work is progressing on an in-house basis thru the reassignment of available manpower. Out-of-house contractor effort will be limited to drafting support. Work to be completed includes layout studies, timing studies, tolerance studies, review of dimensioning, and completion of a full set of drawings.
Development effort was continued on the cycle counter for the XM134. Ninety-five (95) percent of the original drawings were modified to improve the design. Progress has been hindered by the long lead time of required procured components. Three prototype cycle counters have been completed and are currently being tested. One cycle counter is being tested at Springfield Armory and another is being tested at General Electric in conjunction with other G.E. test programs.
A request for proposal for the follow-on development contract was completed and sent to General Electric. The General Electric proposal was received at Springfield Armory. G.E.'s proposed engineering effort was evaluated and found to be reasonable for accomplishment of the scope of work. Preliminary evaluation of G.E. cost estimate and comparison with the Government cost estimate indicated that G.E.'s cost are also reasonable. DCASD (Htfd) is performing a cost analysis and complete audit of the General Electric proposal.
General Electric completed a breakaway and running torque study of the GAU-2B/A gun required by Emerson for the AAFSS project. This study also determined the variations of gun torque when using MIL-L-46000 lubricant and MIL-L-46000 with teflon additive. Breakaway torques were measured at various temperatures.
S.A. completed an evaluation test of a GAU-2B/A gun using a gun housing with minimum modifications required for AAFSS. The modifications require less deep cuts into the ejection port guide, having the same location and width as those originally proposed by Lockheed/Emerson but only to depth of adjacent outer diameter of gun housing. S.A. fired a standard unmodified gun for comparison purposes and took high speed films of the ejected cartridges and cases as they passed over the modified ejection port guide. Modifications to gun housing did not affect the ejection pattern of the ejected cartridges and cases.
A GAU-2B/A gun having a gun housing and guide bar with minimum modifications required for AAFSS has been shipped to Elgin AFB for functional flight testsProduct Engineering Activities:
a. Aircraft Machine Gun, 7.62mm, GAU-2B/A
b. Feeder, Delinking, Aircraft Machine Gun, MAU-56/A
c. Feeder, Linkless
d. Drive Assembly, Electric, Machine Gun
e. Recoil Adapters
f. Pod Drive
g. Pod Adapter
Work accomplished in this period consisted of technical support of Harrington and Richardson, Inc. in the fabrication of barrels; support of General Electric Company in a myriad of technical problems; MRB, VECP, and RIA action; updating of product data, and support testing.
Frequent trips have been made to General Electric Company to provide on-the-spot technical assistance on deviating material by means on Requests for Waiver or Material Review Board actions. Requests for Technical Action have also been received. These trips have resulted in a Springfield Armory representative at General Electric almost every week.
In addition, trips have been made to test centers such as Aberdeen Proving Ground and to Elgin Air Force Base for joint Army-Air Force technical coordination meetings....
PROBLEM AREAS: An interference at the undercut area of the Barrel, F11701204, locking flange was found to be the problem which prevented assembly of many H&R manufactured barrels at General Electric. An assembleability type gage which simulates a max, metal rotor was designed and a number of these were fabricated at the Armory to be used in screening the suspect H&R manufactured barrels.
Hq, AWC requested the Armory to re-evaluate casting classifications and grades on five (5) castings (two gun, three feeder) since General Electric had objected to tighter requirements included in the drawings for the July 66 TDP's. Also, G.E. took exception to the black dichromate finish specified for all 17-4 steel parts since they feel that the 750 degrees F bath causes distortion in the parts.
The five castings were re-evaluated and the Armory recommendations will be forwarded by letter to AWC. The finish question has not been resolved because of a lack of adequate experimentation at either the Armory or RIA.

Notes: "Conceptual and analytical design studies started at General Electric in 1960 as Independent Research and Development projects. Component models were built and tested so that by early 1962 the Minigun design was established. A United States Air Force contract was awarded to General Electric later in 1962 and it called for prototype guns and gun pods.
The first Minigun burst was fired in December 1962; this was followed by the first firing of the gun pod (SUU-11/A) at Elgin Air Force Base in Florida in November 1963.
Both the Springfield Armory and Elgin Air Force Base conducted extensive live firing tests throughout 1964 accompanied by troubleshooting meetings and redesigns with General Electric.
"Side-Fire' which was the application of M37 machine guns firing out the port windows of a C-47 at ground targets was also in test at Elgin Air Force Base. They had difficulties obtaining a desired magnitude of sustained fire power from the M37 weapons. It became apparent to Mr. William Auman, the Air Force Project Officer at Eglin on Miniguns, that the Miniguns could perform like the already proven Vulcans and that the Miniguns could relieve the C-47 'Side-Fire' tests, and provide the needed reliable-sustained fire power. The switch in guns was made. The following tests were successful. The 'Side-Fire' Gunship AC-47 left for Southeast Asia for trials and was in combat with Miniguns by December 1964.
The Miniguns were mounted in their prototype guns pods (SUU-11/A) inside the AC-47 at this time. However, earlier contracts had the improved design SUU-11/A pods in production, so that by September 1965 new pods were delivered to the AC-47 in Southeast Asia. The operation was soon nick-named 'Puff-the-Magic Dragoon' because of the extreme hail of fire that came from the AC-47 during night missions.
The 'Side-Fire' missions were so successful, that by this operation, other applications, and statProduction of Miniguns and various new application system components continues at General Electric. These included pintle mounts and turrets for helicopter, new modular systems for the gun ships and a nose system for the AT-37D fixed wing aircraft.
By January 1971, there were 10,000 Miniguns and 1500 Minipods produced by General Electric. By January 1972, there was recorded 300 million 7.62mm rounds fired on Miniguns....
The Minigun module was also incorporated in the armament system of the two other 'Side-Fire' aircraft, the AC-119 and the AC-130.
Aging Air Force Douglas C-47 transports were armed with three newly-designed General Electric 7.62mm Miniguns with a combined rate of fire of 18,000 rounds/minute were deployed in South Vietnam in the role of long-endurance strike-fighters.
The AC-47, dubbed 'Puff the Magic Dragon' because of the noise and rate of fire of the Miniguns, normally flies at an altitude of 2,500-3,000 ft., well above the range of most small arms fire from the ground....
Puff is a pre-World War II C-47 that someone with imagination outfitted with three gatling-type miniguns capable of delivering broadsides at 18,000 rounds per minute of 7.62mm bullets, tracer or standard.
The guns all point at 90 degrees from the line of flight and deliver the kind of broadsides John Paul Jones would have understood much better than a Korean jet or ace or veteran of the jet strikes in North Vietnam.
Primarily an anti-personnel weapon, Puff circled a beleaguered outpost while the pilot lined up the target in a gunsight pointed out of the left window. Flying at 122 knots, he fired while keeping the left wing low and the piper (illuminated sighting image) on the target. The AC-47 flies at about 3,000 feet, works mostly at night and did not come up against anti-aircraft gunners willing to face her murderous fire.
Capable of circling long hours over a beleaguered fort outpost, Puff can start the deadly circle quickly and in three seconds cover an area the size of football field with at least one bullet to every square feet.
In all, five puffs went through the original test. Later, twenty sisters, in immaculate brown and green camouflage paint, arrived to strengthen the force.
The name traces back to one of the first AC-47 missions when the guns were loaded with all tracer ammunition. Government troops were panic-stricken by the tongues of fire that they saw licking over the ground after Viet Cong.
Calling the plane a dragon, the troops were virtually on the point of breaking and running. Their United States advisers calmed them with assurances that the dragon was friendly, if magic." - George M. Chinn

"...Another 7.62mm machine gun was used by the SEALs in Vietnam, one with probably the longest pedigree of any machine gun in the U.S. inventory. Shortly after the Civil War had begun in 1861, Doctor Richard J. Gatling invented a mechanical repeating weapon that he thought would be so efficient, ti would eliminate the need for large armies. Without the large army, so many men wouldn't have to suffer during a war.
Gatling's idea was to take a series of complete weapon actions and assemble them around a central axis. The use of a hollow cylindrical receiver body surrounding the action with a cam cut into it to guide the bolts would serve to move the bolts back and forth. The lateral motions of the bolts would complete the steps of loading, locking, firing, unlocking, and ejecting as the central axis turned, carrying the barrels and bolts with it. The motive power for this system would provided by the gunner turning an outside crank.
This revolutionary weapon quickly became commonly known as the Gatling Gun. Though few Gatlings were used during the Civil War, the design was considerably changed and refined by Dr. Gatling during the postwar years. The Gatling Gun soon became known throughout the world of the 1800s as a very destructive weapon that could mow down attacking troops like so much wheat.
When the fully auIt was in the post-WWII years that the idea of the Gatling Gun was resurrected. The speed of modern jets aircraft had quickly become so fast that pilots had barely seconds at best to fire at an enemy aircraft before it moved from their sights. Modern automatic weapons did not have a high enough rate of fire to put out many projectiles in the spilt seconds of air-to-air jet combat. A new type of weapon was required.
In the early 1890s, Gatling Guns with electric motors were experimented with by the U.S. Navy and other interested parties. With an electric motor, Dr. Gatling was able to fire at rates approaching 1,500 rounds per minute. This high rate of fire was not needed at the time and the electric Gatlings were soon dispensed with. But ordnance engineers in the 1940s remembered these experimental weapons. In early 1946, a Model 1903 .45-70 Gatling Gun borrowed from a museum was set up with an electric motor drive and test-fired. The 90-year old design reached speeds of 5,000 rounds per minute for a short time.
Further studies of the action determined the Dr. Gatling's original operating principles could reach even higher rates of fire than the tests had already proved. In June 1946, a contract was issued to the General Electric Corporation to design a weapon based on the Gatling multibarrel design that would reach a minimum rate of fire of 1,000-round-per-minute per barrel.
The designs were studied and worked on for several years. In the interim time, several design parameters were changed including adding another barrel to the original five-barrel requirement. A firing model of the new T45 was ready by April 1949. The prototype fired at rates of 2,500 rounds per minute for short times. Further work resulted in fire rates of 4,000 rounds per minute by June 1950. By 1952, the original caliber of the weapons, an experimental .60 caliber round, was changed to 20 millimeters. The new 20mm gun multibarrel was to be identified as the T171E1.
Thirty-three 20mm T171E1 weapons were produced by General Electric between 1953 and 1955. The T171 weighed in at 365 pounds and fired a 20mm ammunition at a rate of 4,000 rounds per minute. Further design changes geared toward a production weapon were incorporated in the new model, the T171E2, in 1954. Problems with the breech of the T171E2 resulted in more changes to stiffen certain portions of the weapon. In April 1956, the T171E3 had been completed which had all of the improvements of the earlier designs. Development of the new weapon was considered complete by December 1956 and production wa begun at a low rate. By December 1957, the T171E3 was designated the M61 Vulcan cannon and production was speeded up.
The M61 Vulcan could fire 20mm explosive ammunition at rate of 6,000 rounds per minute. The basic design of the system was still centered on Dr. Gatling's multiple barrels and actions revolving around a central axis. A helical cam path operated the bolts through the cycle. As long as the barrel turned, the bolts moved back and forth in their rotor tracks (slots). Feeding of ammunition was accomplished by an external feeder attached to the receiver of the Vulcan and driven by a gear arrangement connected to the main drive system.
The Vulcan was considered one of the most dependable and safe 20mm cannons in existence. If a round misfired, it would be extracted and ejected outboard, away from the weapon. No interruption in the cycle of the weapon would take place since the system was not dependent on the firing of a round to operate. Other designs followed the success of the Vulcan, with the new weapons increasing and decreasing in caliber.
In 1960, General Electric began looking into adapting the Vulcan design into a .30 caliber externally powered maThe bolts of the Vulcan lock directly into the end of the barrels for various mechanical reasons. The smaller version of the Vulcan didn't require such a locking system. The bolts to the new weapon were made in two parts, one (the bolt body) camming a twisting motion into the other (the bolt head). As the bolt head rotates and locks into place, the firing pin is cammed and released, firing the percussion primer of the ammunition.
The U.S. Air Force became interested in the new design and issued a contract for prototype guns and aircraft gun pods to be developed. By December 1962, the new weapon, christened the Minigun, was ready for test firing. The first gun pod (the SUU-11/A) was ready within a year and was demonstrated to the Air Force in November 1963. Extensive testing of the new Minigun was conducted by the Air Force and Springfield Armory. Redesigns were completed by General Electric to eliminate problems in 1964.
The final design of the Minigun was of a six-barreled weapon that could fire at various rates up to 6,000 rounds per minute. The rates of fire were modified by either changing the motor which drove the Minigun, or by changing the gear ratio in the drive train between the electric motor and the weapon. The Minigun has fixed-headspace, quick-change barrels and the entire weapon could be stripped down to it essentials easily.
An external feeder takes standard, M13 linked 7.62mm NATO (M60) ammunition and strops the rounds from the links. The feeder dumps links outboard and loads the incoming rounds into the receiver. The feeder can also stop feeding rounds into the Minigun before the barrels have stopped rotating. This allows any ammunition in the weapon to be cleared from the gun when the trigger is released.
A new application of the Minigun was soon tested after the final design was completed. Mounting three Minigun pods in the body of a C-47, pointing out the left side of the aircraft, created a new kind of attack aircraft. The new AC-47 Gunship could fly over a target on the ground, bank and turn the aircraft, and fire the Miniguns into the target. The new application of the Minigun was devastating in tests.
By December 1964, the new AC-47 gunship design was in combat in Vietnam. The new gunships were nicknamed 'Puff the Magic Dragon' after the popular song of the period. The Viet Cong likened the aircraft to dragon breathing fire at the ground and simply called them Dragon ships. For many SEALs, their first introduction to the Minigun was due to a Dragon ship.
'When that AC-47 gunship banked over the target on her left side, I could see why the VNs held the craft in almost superstitious awe. The three 7.62mm Miniguns pointing out the side of the plane poured out their fire with a thrumming roar. The Miniguns fired so fast that the sound wasn't recognized as a weapon. It sounded more like a long, deep note from a gigantic base fiddle, or maybe the roar of a flying dragon.
Each of the Miniguns would spin its six barrels, spewing out steel-jacketed death at a rate of 6,000 rounds a minute. Eighteen-thousand rounds a minute would pour from the side of the plane, every fight round a tracer. The tracers would burn out before hitting the ground from Spooky's attitude of 3,000 feet.
Looking up from the ground, all you could see in the darkness was a moving black shape against the stars, licking down at the ground with three long fuzzy red tongues of flame. In a single pass, Spooky could cover an area the size of a football field in three seconds, putting at least one bullet into each square foot of ground.'
... The psychological effect of incoming fire from a Minigun was devastating on the Viet Cong, or anyone who was on the receiving end. Reports had come out of Vietnam that enemy snipers would ignore incoming .50 caliber machine gunfire and would continue firing on U.S. forces. As soon as the Minigun openeThe bright red streak of the tracers from the Minigun, coming in at such a fast rate they appeared as a fuzzly line, also added to the mental impact of the weapon. SEAL and BSU gunners who used the Minigun developed a strong confidence in their weapon; the enemy who faced the Minigun feared it just as strongly." - Dockery

"This multiple-barrelled 'Gatling' pattern machine-gun is based on the 20mm Vulcan development and was specifically designed for use in helicopters in Vietnam. Due to its demands for power and ammunition its application is restricted to helicopters or vehicles which provide the necessary space and electrical source. The six barrels are revolved by an electric motor; they are normally parallel but can be clamped into various degrees of convergence as required. The action body, behind the barrels, carries six bolts in a rotating unit; these bolts lock into the barrels by rotation of their heads, controlled by studs moving in a cam groove inside the receiver. The ammunition is belt fed into the action body, the rounds are stripped out and positioned in front of the bolts, and as the bolt unit revolves so each round is chambered. At the uppermost position of the barrel the firing pin is released and the round fired, after which the empty case is extracted and the bolt makes a complete circuit to pick up another round. When the trigger is released the ammunition feed is isolated so that there is no danger of a cook-off during the short time the barrel and bolt assembly is coming to rest." - Hogg & Weeks

"With the M61 cannon in series production, development engineers at General Electric began to examine the possibilities of constructing a similar gun in rifle calibre. The US Air Force-funded project got underway in 1960, and by late 1962 a prototype was under test; two years later the GAU-2B Minigun, firing the 7.62mm x 51 NATO round, was adopted. The Miniguns were mounted in SUU-11 pods designed to be slung beneath the wings of aircraft or on the undercarriage of helicopters, but the first combat operations in which they participated saw three of them mounted transversely inside the fuselage of an antiquated C-47 Dakota, firing out through what had originally been the aftermost cabin windows and the cargo door while the pilot executed a tight 'pylon turn' around a ground target below. Widely known as Spooky or Puff the Magic Dragon, from a song popular at the time, the AC-47s soon proved to be effective ground attack aircraft, and the concept was expanded and extended, firstly into Shawdow and Stinger and subsequently into Specter, converted C-130 Hercules, initially armed with four Miniguns, two of which were later removed and replaced by a pair of 40mm Bofors or occasionally, in the Pave Aegis version, by one Bofors and a specially adapted M102 105mm howitzer." - Roger Ford

"Finally, we arrived at Da Nang, Vietnam, just in time for a firefight. The fight was going on all around us, and the Cobra gunships and Spooky were working the area near the base. It was quite a first impression of Vietnam, seeing the miniguns fire from Spooky, the AC-47 gunship. Spooky was a reconditioned cargo plane, a DC-3, that had been fitted with three 7.62mm miniguns that fired out of the port side of the plane. Each gun could fire fifteen hundred rounds in fifteen seconds, with every fifth round being a tracer.
Watching from a distance, the effect was neat. You would see this red light extend down from the sky and lick at the ground and then disappear as its tail left the plane and went down. Then you would hear the noise of the guns firing. Not the sound of a regular machine gun. The miniguns fired so fast the sound blended together into one long WHAAAAAAA. It looked like some type of laser tag was being played with the VC. It was strange and a very strong first impression of Vietnam." - Commander Larry Simmons, USN, Ret.

SLANG - "Dragon ship - 1. slang for a transport plane converted into a GUNSHIP, an aircraft fittGo-Go Bird - nickname for CH-47 helicopter modified for close air support, with two 20mm Vulcan guns, .50 caliber MACHINE GUNS and 40mm GRENADE LAUNCHERs. Also called hook, the shithook, Go-Go ship, or simply Go-Go."
Puff the Magic Dragon - "nickname for the C-47 with VULCAN MACHINE GUNS set up in the cargo doors. It provided intensive ground fire, with MINIGUNS and FLARES. Also called Puff, Dragon Ship, and Spooky." - Dr. Linda Reinberg

Chinn, George M. THE MACHINE GUN. Vol. V. Edward Bros. Publishing Co. Ann Arbor, Mi. 1987.
Dockery, Kevin. WEAPONS OF THE NAVY SEALS. Berkley Books. N.Y., N.Y. 2004.
Hogg, Ian & John Weeks. MILITARY SMALL ARMS OF THE 20TH CENTURY. 6th Ed. DBI Books, Inc. Northbrook, Il.
Reinberg, Ph.D., Dr. Linda. IN THE FIELD: THE LANGUAGE OF THE VIETNAM WAR. Facts on File. N.Y., N.Y. 1991.

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