Knob Creek ’13- Hello, M134 Mini-gun

Now we’re talking. The M134 fires 7.62x51mm NATO rounds at a variable rate of 2,000-6,000 rounds per minute. It’s gatling-style six barrels are spun using an electric motor designed by General Electric and other brands. It makes a very distinctive “zipping” noise when firing. Here’s an example I randomly found on YouTube:

And here are more pictures of the one I saw on display at Knob Creek:

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This one wasn’t for sale, but it sure was fun to look at.





Chris Cheng

Chris Cheng is History Channel’s Top Shot Season 4 champion and author of “Shoot to Win,” a book for beginning shooters. A self-taught amateur turned pro through his Top Shot win, Cheng very much still considers himself an amateur who parachuted into this new career.

He is a professional marksman for Bass Pro Shops who shares his thoughts and experiences from the perspective of a newbie to the shooting community. He resides in San Francisco, CA and works in Silicon Valley.

www.TopShotChris.com.


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  • Clint Notestine

    looks like its seen plenty of use πŸ™‚

  • Vhyrus

    I would give anything for a working model of one of those.

  • Geoff a well known Skeptic

    Mythbusters favorite auto weapon! Of course back in the Viet-nam era, we had duplex ammo for it as well. Two! Two! Two bullets in one case! Geoff Who notes Dillon reverse engineered the piece from a semi working example.

  • Geoff a well known Skeptic

    Ah, isn’t the google wonderful, eventually: http://nerds-central.blogspot.com/2008/02/kari-cuts-down-tree-with-m134.html Geoff Who wouldn’t mind being the ammo bearer for that show!

  • DiverEngrSL17K

    Thanks for the detailed photos, Chris — nice work. Wish I could have attended the show.

    Aside from the fact that externally-powered mechanical guns like the M134 are dependent on a power source — which makes them better-suited to platforms such as AFV’s, helicopters and fixed-wing aircraft that are able to consistently and reliably supply that power while coping with the added weight penalty — many people also forget that there is a fractional pause before actual firing takes place when the trigger is first activated because the electric motor that drives the barrel cluster has to spool up. Similarly, there is also a fractional over-run, during which extra rounds are cycled and fired, after the trigger is released and as the drive motor spools down.

    On the other hand, a big advantage of a mechanical gun is that defective rounds that FTF will not stop the action since they are simply ejected as the firing cycle continues unabated.

    • Glad you enjoyed the pics. You definitely need to come one of these years!

    • gunslinger

      being a controls engineer, i must wonder if this is truly accurate. now yes, i can buy the “spool up” time. but the post firing is what gets me.

      i only ask because is there a disconnect betwee the motor turning the barrels and the firing pin striking? because i can see the barrel turning, and the FP not engaging. after the trigger is released. because the time for the electronic signal to travel is “instantaneous” which would disable the pin, while leaving the motor to “wind down”

      can anyone give more detail?

      thanks

      • disqus_PIBlw47Tej

        Seeing this gun operate at knob creek a few years ago I noticed that most of the rounds ended up in the dirt before getting on target. It ran dry very quickly. The coolest guns were the .50 cal M2 and the WW1 era guns. They were on target in a few shots and rocked those junk cars like nobody’s business.

      • Ripley

        Here you are; a beautiful ultra slow motion from last year’s KK. http://youtu.be/lVgTTAukMOU

        Basically the ammo delinker/feeder and the gatling function are separate so that it only feeds when the rpm is in a good range. So when the firing trigger is pressed it spins up for about two rotations before engaging the ammo feed. Then after the trigger is released it will stop feeding and disengage the gatling motor while the last chambered rounds will fire and then it just spins empty for a few seconds. Probably, but I’m not sure, the firing pins are not mechanically engaged if the feeding isn’t on.

        • gunslinger

          looking at it, i can see how it takes about 2 rotations before the first round is fired. however it’s hard to tell when the triggrer is released and the last round fired.

          from above it sounds like the firing pin is only mechanically triggered based on rotation. i.e. every time a barrel moves past the “firing position” the firing pin will release, no matter if there is a round or not..if it is ramping up, at speed or ramping down.

          • DiverEngrSL17K

            Exactly.

          • Ripley

            Yes the gatling principle intrinsically connects the rotation to the firing and extraction. There are fine videos about it. But the original gun was hand cranked, would not spin freely, and wasn’t spinning at crazy speed. Feeding the gun during ramping up would probably be very tough on the motor and perhaps induce feeding problems.

            I know that the shooters at Knob Creek are instructed not to burst fire with that gun but only shoot it until empty. I think the feeder turned off the motor when the ammo was empty – before the shooter even reacted and released the trigger.

        • DiverEngrSL17K

          Good link and great commentary. It still doesn’t change the fact that there is an inherent fractional hesitation during start-up and a fractional “rounds out” over-run during spool-down of the barrel cluster in an externally-powered gun. In most operational scenarios, this is not a real issue. However, there has always been, and still is, some concern about the ( admittedly, split-second ) reaction time difference in start-up, especially in close-range air-to-air combat, where tiny fractions of a second can make a difference. On the positive side, improvements in control circuit and solenoid technology have closed the gap somewhat in recent years.

          • Ripley

            I don’t think the remaining rounds are any issue at 4000 rpm. There are only six barrels which I believe two or three are already in extraction phase. But yes the gatling (any) is not something you snipe with. Targeting computers have made the aircraft guns easier to use than when they were first introduced and I don’t think pilots today have to think much about the delay. I don’t know if the M61A2 made any changes to the A1 except shaving weight. Otherwise the designs are pretty much unchanged for decades.

      • DiverEngrSL17K

        Hi, gunslinge :

        That’s an excellent and perceptive inquiry that you’ve made.

        In a typical Gatling-based, externally powered rotary weapon design — including the 7.62mm M134, 20mm M61A1 Vulcan and 30mm GAU-8A, among others — each individual barrel assembly in the cluster is actually a complete gun mechanism in its own right, inclusive of firing pin and breech, but minus the feed mechanism. As the barrel cluster is electrically rotated inside the external cylinder body ( synonymous with the receiver on a conventional machine gun or automatic cannon ), each barrel assembly rotates up into the “feed” ( call it Top Dead Center or 12 o’clock, for the purposes of this discussion ) position, and a cam head in the firing pin assembly engages a corresponding slant-cut groove in the external cylinder body. It is from this point onwards that a purely mechanical action takes place. A cartridge is then pulled from the feed belt into the breech. As the individual barrel in question rotates into an intermediate ( call it 3 o’clock ) position, the firing pin comes forward in its cammed groove in the breech mechanism to strike and fire the cartridge. When that individual barrel rotates to the “eject” ( call it 6 o’clock ) position, the empty cartridge is ejected out of the gun. In the meantime, the next barrel assembly has followed the same sequence and continued the overall firing cycle. Obviously, the relative mechanical positions for “feed”, “fire” and “eject” can be varied to some extent by changing the shape and position of the camming grooves in the breech bodies.

        This is why there is a fractional over-run whereby some extra rounds are fired before the drive motor and, by extension, the entire rotating barrel cluster can come to a full halt after trigger release. Remember, the trigger actuation is not mechanical but electrical, and really constitutes the closing and opening of an electrical circuit to activate or de-activate the drive motor. The individual barrel assemblies will continue to function mechanically as designed — to chamber, fire and eject cartridges — as long as they rotate past the “feed”, “fire” and “eject” points in the external cylinder body. It is only when this rotation comes to a full stop that firing will also come to a halt. Since the electric drive motor takes a fraction of a second to come to a full stop after trigger release ( when the circuit is cut, i.e., put in the “open” position ), there will be a certain fractional period of over-run firing.

        An interesting approach to eliminating the momentary lag in he start-up and shut-down phases of the firing cycle was adopted by the Soviet Union in weapons such as the Gryazev-Shipunov GsH-6-23 23mm and GsH-6-30 30mm rotary aircraft cannon, which have been in standard service with the Soviet ( and now Russian Federation ) Air Forces for several years. Rather than rely on an external electrical, hydraulic or pneumatic power source, the GsH-6-23 and GsH-6-30 ( and other derivatives in an assortment of different calibers ) are gas-driven. While it is much more challenging up front to properly manufacture and time a multi-barreled gas-operated rotary gun, the pay-offs are definitely worthwhile — no spool-up or post trigger-release lag time, no reliance on external power sources ( with their attendant complications and vulnerabilities ), and reduced overall weight and bulk resulting in lighter and more compact installations ; and all this while still retaining the major advantages of a Gatling-type system — no stoppages from individual FTF’s, extremely high rate of fire, excellent reliability, and little to no overheating during prolonged firing ( since each barrel fires once in a complete rotary cycle, with ample cooling time in between ). All evidence indicates that the Soviets / Russians succeeded admirably in their quest for a reliable high-performance gas-operated rotary cannon / machine gun to the point where this may be one of the most widely-reported yet under-appreciated facts in the West.

        To be fair, several U.S. designers and manufacturers had, over the decades, come up with prototype gas-operated versions of the standard electrically-powered rotary weapons in regular service but few, if any, have been adopted, probably because the U.S. Armed Forces had already long since been deeply committed in terms of both systems adoption and logistical entrainment to the externally-powered versions. As usual, this spells out as a MAJOR financial investment, and it is understandable why it is so difficult to change course in mid-stream at this level. Add to this the fact that the U.S. has achieved long-term familiarity and a very high level of expertise with externally-powered guns, and the resistance to change is all the more compelling.

        Hope this helps to answer your question.

        • gunslinger

          I guess that’s basically what i was asking. was the firing pin mechanically related to the rotation of the barrels or if it was independently controlled via electronics from the trigger.

          i.e. when going to the 3oclock position, does an electrical signal trigger a “release” of the pin? it sounds like it doesn’t. from what has also been stated, that as long as a bullet is chambered and the barrel rotates to that specific position, the bullet “will” fire. it sounds like if the gun isn’t moving at a certain speed, there is another mechanism that will prevent a bullet from being loaded.

          as i said, i’m a controls engineer, and have done high speed motors for packaging and high torque motors for steel processing πŸ˜‰

          • DiverEngrSL17K

            I think you’ve grasped the general concept very nicely. What throws a lot of otherwise well-informed people is the transition point between externally-powered rotation of the barrel cluster and where actual mechanical actuation of the feeding / firing / ejection sequence for each individual barrel assembly takes place. To put it another way, the external power source serves only one function — to maintain the firing cycle for as long as the trigger is engaged ( and rotational power is maintained ). Within each each rotational cycle, the individual barrel assemblies mechanically feed, fire and eject independently. They only stop when the external power is cut off and the barrel cluster stops rotating. If there is a start-up lag or run-on in the external power source, the rotational cycle will be affected accordingly and the individual barrel assemblies will continue to function until they come to a full stop.

          • gunslinger

            yeah. that’s it. i didn’t know if the pin was mechanically or electrically triggered

          • DiverEngrSL17K

            You’ve got it right. The firing pin function is part of the purely mechanical function of each individual barrel assembly.

            Bear in mind that another factor that also confuses many people is the fact that certain modern Gatling-type weapons use electrically-primed ammunition. This feature can be used on externally-powered as well as self-sustaining ( gas-operated ) guns. This does not change the basic operating principles we have previously discussed. It simply means that, instead of having to kinetically ( mechanically ) strike the cartridge primer in order to ignite it, the firing pin simply has to make contact with the primer, at which point an appropriate electrical charge coming through said firing pin will provide the means for primer ignition.

            Whether one should use a purely mechanical means or electrical means of primer ignition would depend on an in-depth analysis and sufficient proof-testing for the anticipated application involved, taking into account all known and anticipated design and operational factors.

          • DiverEngrSL17K

            You’ve got it right. The firing pin function is part of the purely mechanical function of each individual barrel assembly.

            Bear in mind that another factor that also confuses many people is the fact that certain modern Gatling-type weapons use electrically-primed ammunition. This feature can be used on externally-powered as well as self-sustaining ( gas-operated ) guns. This does not change the basic operating principles we have previously discussed. It simply means that, instead of having to kinetically ( mechanically ) strike the cartridge primer in order to ignite it, the firing pin simply has to make contact with the primer, at which point an appropriate electrical charge coming through said firing pin will provide the means for primer ignition.

            Whether one should use a purely mechanical means or electrical means of primer ignition would depend on an in-depth analysis and sufficient proof-testing for the anticipated application involved, taking into account all known and anticipated design and operational factors.

  • Anonymoose

    I heard there are like 5 registered pre-86 M134s, and they go for over $10000 when people actually put them up for sale.

    • BryanS

      add a zero.

      • Anonymoose

        derp.

    • DiverEngrSL17K

      Beautiful and deadly, but too rich for my blood ( and bank account ) :).

  • RocketScientist

    Just some numbers fun to put the awesomeness in perspective: at max rate of fire, thats 100 rounds PER SECOND. A one second burst gets you a constant line of bullets about 10 football fields long, with a bullet spaced every 10 yards. Each of those bullets has about the same kinetic energy as an R1 motorcycle moving at 20 mph.

    • DiverEngrSL17K

      That’s assuming a mostly linear perspective. The barrel clamps on any Gatling-type rotary automatic gun, regardless of type or origin ( eg., 7.62mm M134, 20mm M61A1 Vulcan, 25mm GAU-12, 30mm GAU-8A, 23mm GsH-6-23, 30mm GsH-6-30, and so on ) can be adjusted to provide the desired changes in shot dispersion in both planes.

      As for the kinetic energy analogy, how about Jorge Lorenzo and the YZR-M1 GP bike traveling at 200+ mph on a closed-course road-racing circuit such as Misano, Catalunya or Losail? πŸ™‚

  • bradtmiell

    Can anyone please explain to me the physics of a mini gun with both 7.62x51mm cartridge? A real bonus would be the physics with tracer bullets also

    • gunslinger

      what do you mean by “the physics of…”?

      • bradtmiell

        like how the projectile is released and how the gun chamber sustains the produced energy etc. Any help is good help πŸ™‚

        • bradtmiell

          the kenetic energy specifically etc

          • gunslinger

            shows how the gun loads, fires and ejects a round.

            http://www.youtube.com/watch?v=d84r8gMGxFQ about 1:41 into it, you can see the barrels start to get red hot.

            the minigun is an electrically driven device, i.e. there is an electric motor that spins the 6 “guns”. as discussed below, as they rotate, they pick up a bullet, the bolt chambers the round, then the firing pin is released, and then as the gun barrels rotate, the bolt pulls back, ejecting the round. the barrel rotates again to the “pick up” position and starts the process again.

            I’m going to guess that the “recoil” is not felt because of how locked down (fixed position) the gun is. see the FPSRussia video again and notice the non-recoil. I don’t know if there is a damper or something, but from the first video, i don’t think there is. I want to say the rotational energy is somehow compensating for the “recoil”

            As for the high rate of fire, remember, each barrel is only firing once on a revolution, so it’s 1/6 of the RoF. So if the minigun is about 4k/min each barrel is only going about 667 round/min. very slow..comparitivly. but as was shown, sustained fire will still cause the barrels to heat up/glow.

            hope this helps.