Pancor Jackhammer

The Pancor Jackhammer was a select-fire combat shotgun designed by John Andersen in the 1980s. He was a Korean War veteran who had used a pump shotgun in combat, and while he liked the shotgun concept, he felt there must be a more efficient way to make a shotgun than a single-loading pump action. The tinkered with ideas and designs, and ultimately devised the Jackhammer. It is a remarkably clever and interesting mechanism, combining mechanical elements from the Mannlicher 1894, 1895 Nagant revolver, and the Webley-Fosbery automatic revolver.

After making several dozen mockups out of wood and clay to get the mechanics just right, Andersen built a fully functional prototype, which is the gun you see here. It used a lot of large cast parts (and weighed a fully 17.5 pounds), and had a very slow reloading process. However, it proved that the concept was valid and it worked reliably. Andersen then made two more with much lighter materials and a much improved reloading mechanism. These two guns were submitted to the US military for testing, and both were ultimately destroyed by HP White Labs in destructive tests. The testing proved very positive (the guns survived a 50,000 round endurance test), but were ultimately rejected by the military.

The first prototype was kept personally by Andersen, and is now the sole existing Jackhammer. It was owned for several years by Movie Gun Services, which rented it to a number of film, video game, and comic book companies. Because of this and its very distinctive appearance, the Jackhammer has made appearances in a vast number of comics and video games.

Thanks to the folks who kicked in to my IndieGoGo fundraiser to help me make the cross-country trip to film this gun! I was not able to shoot it for liability reasons (the owner was not present and the gun most recently sold for $135,000), but I hope you will enjoy getting an in-depth tour of how it works.


  1. A select fire smooth-bore shotgun revolver with enough shields to keep ones forearms from being burned from the required cylinder to barrel gap.
    Should have had a quick center pin release to pop in another cylinder.

  2. Interesting but I still prefer the later-model Atchisson Assault Shotgun (Double-A 12) with the closed bolt and gas piston. One reason is the 20-round drum magazine for more fire power but at the expense of a much heavier weapon. It also was able to handle much more powerful loads of “specialty rounds.” But I like the option of the pump-action cycle in case it is needed. This brings to the forefront the instructions of, “In an entry operation, if you encounter two targets one with a SMG and the other with a shotgun, kill the shotgun first; he is the most dangerous in close quarters.” A full-auto shotgun multiplies this by several orders of magnitude.

  3. Bo bo bo boner! Thank U!

    A few questions:
    Some sources claims that the drum ‘magazine’ designed to be pre-load with shots/slugs gunpowder and primers and empty or half empty drums meant to sent back to factory for re-load like modern day recycled glass bottles! How much true are those claims?
    Some sources also claims that the fully automatic Jackhammers didn’t had fire mode selector…instead firing single shots been done by quickly release of the trigger, the firing rate is slow compare with most automatic guns so a skilled shooter can firing single shot
    Is it true?


    • I think the factory-packaged ammo was an idea for production, but not the reality of the prototypes. It may well have been the notion of supplying pre-loaded and disposable mags, rather like the initial plans for the AR.

  4. Fascinating.
    I was mesmerized!
    I’m not a shotgun guy but would like one of them.
    Are there any videos of it firing, especially on full auto?
    Some company should get the patents and resume development
    with a military application.
    Would be a great SWAT-attack-assault weapon.
    Solo mis dos pesos

  5. The whole thing (or practically) the whole thing could be made outta polymer today…it’s be nice to see Kel-tec or mebbe Glock??? come up with a remake of this, but with a box bagazine…

    • Treeby chain gun… Er, hollow the mag out “to a cylinder” with supporting pieces at either side, then a belt of said chambers rotating within.

      • No that’s not right, but… The principle is basically sound, with some modifications. You have this cylinder rotate an axis pin that turns a treeby “belt” with titanium chambers.

    • Iirc, part of the plan was to use one of the Du Pont fibre reinforced polymers for significant chunks of the gun.

      Unfortunately the DoD made sure that Anderson as an upstart, went bust, before it got that far.

  6. Awesome video. Thanks for is and all the rest of your videos.

    One question RE: weight and that forward barrel gas op design. With the barrel/op rod assemblies being pushed forward along with the shot and shot cup, wouldn’t the recoil have been substantial? I understand that the weight, especially with that prototype, would have been a nice inertial dampener for this, but it seems like full auto with that would require a very efficient muzzle brake to combat both linear recoil and muzzle rise.

    Do you have any thoughts on this, Ian?

    • Yes, the forward-moving barrel would definitely increase recoil, all else being equal. The weight of the gun probably did a lot to compensate. I am told that recoil was significant, but not uncontrollable.

    • Have a counter recoil thing… Like the Ak107, but the other way round i.e. This barrel moves forward, so the counterweight would move rearward- Rack and pinnion or something.

      • The barrel moving forward is a good idea, with a revolver type design because you get the gas seal thing, which holds the cylinder in the correct place also.

      • Unfortunately Newton’s “for every action there is an equal but opposite reaction” cannot be avoided

        With a blow forward, the gun and the firer’s shoulder get the reaction to the barrel moving forward

        And that is in addition to the reaction to the shot load and propellant gas coming out of the barrel that you get with any gun.

        The only options are to spread the impulses over a longer time period, for example Becker/Oerlikon open bolt with advance primer ignition, and Solothurn 20mm anti tank cannon, which ran the whole action forward before firing.

        Or to harvest some of the remaining energy from the escaping propellant gasses, with a very efficient muzzle brake, which is difficult on a shotgun, due to shot, low muzzle pressure, and relatively large diameter, then add in the mechanical problems of fitting a brake to a forward moving barrel. Plus a muzzle brake subjects the firer and anyone either side, to vastly more noise.

        Blow forward has some potential advantages, particularly for compact guns, and allowing gas sealing, as the jackhammer does, but increased recoil seems to be one of the unavoidable prices to pay.

  7. Wow. Considering all of the “pop cultural references” to the Jackhammer, I’d always figured there had to be a FEW of them out there. I learned something new.

    If someone cleaned up the design with some modern materials, dumped the bulky rotary magazine for a stick magazine a la Saiga, maybe lose the full auto, a rail for sighting systems, and you’d have a formidable weapon.

  8. The very first thing I notices was the similarity to the Webley cylinder…. Gotta admit based on having that pistol in my head the mechanism here is far from what I was expecting. Really neat gun and it’s a shame no one is reproducing them.

  9. I always thought the Jackhammer concept made more sense as a grenade launcher. In fact, the U.S. Army experimented with a similar concept back in the 1960s.

    Today, the USMC has the Milkor MGL aka M32 40mm grenade launcher, which works on basically the same principle;

    It occurs to me that a Jackhammer-type 40mm MGL would be even more compact than the M32, due to its bullpup layout.

    Also, imagine a “mine cylinder” loaded with 40mm flechette rounds and/or “Bouncing Betty”-type airburst munitions instead of 12-gauge buckshot. (Suggested nickname; The Shredder.)



    • There’s some decent 20mm projectiles “Short, 20mm” grendade case things, which can be potent particularly if accurately fired with adjustable fuses to achieve air bursts at the correct point.

    • There was a film in the 80s with a scene of a loan man with some revolving cylinder shotgun/grenade launcher, destroying a convoy.

      All good Hollywood fantasy BS.

      Almost immediately, “revolving shotguns” were banned in Britain.

      The only revolving shotguns on the market at the time were Italian made smooth bore ” buntline special” reproductions.

      IIRC, they might even have gone as big as .410. 9mm flobbert rim fire was more likely. Instead of a name like Jackhammer, they were called “the ratter”.

      Fact never did get in the way of either Hollywood fiction, or British anti gun legislation.

  10. Holy cow! What an awesome and informative video! I’d long assumed that there were more extant prototypes than just the “one.”

    So, if two other prototypes went through a 50k 12-ga. 2-3/4″ round count successfully, does that mean that the Pancor Jackhammer has proven the viability of the “blow forward” design? I mean, no one wants to do a 50k test with that awkward little .32 acp/7.65mm Steyr blow forward pistol, and it has sharp recoil in spite of the somewhat anemic load… But still.

    I note that there was a Coenders blow-forward 7.92x33mm carbine that was “tool room prototyped” for the last-ditch Nazi Volkssturm militia. It was loaded with a 5-round charger/stripper clip into a fixed magazine, and used a blow forward system, although without the same gasket type system as the Jackhammer there… Might be what was required to make it work…?

    So, Ian, are you going to be allowed to head over to Crye and do a preview of the mechanisms of the Six12? Might be interesting to see how the double-action revolver is going with a six-round metal cylinder of 12-ga. shot shells… I’m not sure how many will sell since they’ll be competing against the straight-pull bolt-action M26 under-hammer with five-round box magazines.

    Either way: Crye Six12 revolver or M26 straight-pull in a legal “stand alone” version, and I’ll forget about the Ithaca Auto & Burglar!

    Oh, and yes, this is THE reference for the Pancor Jackhammer! Thanks!

    • “the viability of the “blow forward” design”
      In Soviet Union in 1930s self-loading with forward-backward moving barrel rifle was tested:
      Автоматическая винтовка системы Мощевитина образца 1934 г.
      (Automatic Rifle Moshchevitin system Model 1934)
      However it was not plain blow-forward but has locking system, it has awful recoil (even more recoil that Mosin Cossack), in full auto it fires 1400 rpm. On other side it was most reliable from all automatic rifles tested, failure to fire chance was 1-2%. GAU (Main Artillery Directorate) ordered development of special purpose machine gun from rifle, rifle development was abandoned.

      • “When fired, the barrel initially received a small rotational movement and is released to the receiver, and then rolled back forward until failure, then ejected cartridge cases, cocked hammer mechanism, the spring receiver returns back to the trunk of combat visor receiver; if this movement is coming to the cartridge barrel, rising out of the store, and charged, and then a few turns to the right, grappling with the receiver.”
        These automatic translators aren’t much help, he he.

    • Also the SIG Ak53 was a Swiss locked breech forward moving barrel assault rifle development.

      Ian has some information on it in other posts

  11. Sorry, but it looks a car rided over a carrier and giving the mobility with its tracking wheels. Completely a waste of mind and material for military porposes but a tressure for fictive world. Doctor’s order for movies, however. IMHO.

    • Shotguns found a military use again, in Afghan compound busting, and in built up areas of Iraq… And this, in a finished version is surely a better tool for the job. Fun switch on, bust the door, and spread the love.

          • If I am not mistaken current-issue USMC shotgun is M1014 (other designation: M4)
            which feature tube magazine. I don’t known post-Korean War infantry weapons of USMC history well, but I hope that somebody will point against which other shotguns designs M1014 was tested before choice – does it contain box-magazine shotguns?

          • Boxs are quicker to reload, than tube magazines, but the drum is a type of box in that sense if it’s quickly detachable.

          • Idea with a tube magazine is that one on the top it off on the go. A lot of people grew up duck/dove/quail/rabit/pheasant hunting and did just that to keep them topped of. Birds show up, bang bang, then shove in two more shells without really thinking about it. One can burn through a box of 25 in short order if the birds are really coming in. If the gun runs out completely, then pull the slide back and drop a fresh shell in the chamber and push the slide foreward. A tube gun should never be empty for more than a second or two so long as the user has ammo, they are not going to be caught with their pants down while swapping out cylinders or boxes.

            Magazine guns are surely better if one has to dump a whole magazine, and then can take cover to replace the magazine. If it is a case of shoot three times, take cover and move, shoot four times then take cover, move around then shoot four times, etc., then a tube gun makes some sense.

            This would be a great topic for a match between Ian and Karl.

  12. Odd thought, due to the camming mechanism, Unlike a regular revolver, you should be able to use a smaller cylinder [or larger] just by switching the center pin location…
    I could see some possibilities for that [small 6 shot or even 3 shot for hunting, large 10 or 20 shot for combat]

    Just a thought

  13. Weapon of choice scenario:

    As a shop keeper, how do you stop looters who take advantage of some random politically charged riot just to rob your store?

    1. Pancor Jackhammer or Ithaca Auto & Burglar
    2. 1950’s police electric riot gloves (1500 volts of PAIN)
    3. Pepper blaster (think pepper spray in a firearm cartridge)
    4. Lebel with ludicrously powerful search lamp (referencing the post “Spare a light?”)
    5. German (or Alsatian) Shepherd from behind the counter
    6. Katana [evil laughter]
    7. Beretta MAB 38 or MP-34 (O)
    8. flash bombs or tear gas
    9. Sturmgewehr
    10. Water cooled variant of the MG-15 with doppeltrommel or MG-34 with the same kind of ammo drum
    11. Trapdoor of doom in front of the counter (when a thug tries to grab the cash register)
    12. ASP from a fake book
    13. Stechkin OTs-38
    14. Mondragon rifle with drum magazine
    15. Screw rummaging! I OWN THE GUN STORE! (add your favorite toys or your customer’s toys to this list)

    This activity is totally voluntary. You are not required to participate if you do not wish to do so. Please keep any criticism of this post humane and free of foul language.

    Thank you,


    • I’d utilise the trapdoor of doom, you could keep placing money on the counter. And going “Help, help! Take it, take it!!” Then pull the lever, wait for AIIIEEE! and have a snigger to yourself repeatedly. Keep the Jackhammer at hand though, incase there’s multiple theives rioting in your shop. It wouldn’t have any piranhas or sharp sticks inside it, it would be a black void of nothingness… The shop would be built over a very deep mineshaft you see, around the trapdoor. I wouldn’t own a shop without one frankly, nattering old ladies, crying children and such. I don’t own a shop, incidentally.

      • It goes without saying it is important to have a strict regime of testing and maintenance for a trapdoor of doom. I’ve thought about having one but when I looked into it there didn’t seem to be any local tech support.

        • Did you contact your local carpenters, electricians, and plumbers? They could build a trapdoor into the foundation of a building given the right materials. Why the plumber? If you don’t have a mineshaft for the trap, just have the chamber flooded at the opening of a water valve. The cops will literally fish the crook out and the crook will be unable to shoot or stab anything, having been half-drowned for at least ten minutes…

          • It seems to be a lack of expertise in the trigger mechanism which is the problem locally. A small local supermarket was left in the lurch by a tradesman who over estimated his talents. They dug out the 10m deep pit and filled it with water, stocked it with goldfish to keep mozzies out. Tethered a bunch of tiger snakes around the edge of the hole and built a very well concealed trapdoor but the shoddy workmanship on the mechanism has lead to sudden openings so now it’s a great big hole right in front of the front counter. It was all cash in hand so they don’t have any recourse.

          • @Tassiebush

            Okay, you may need an expert in electrical triggers. In a well defended store, the clerk would step on a foot-pedal to complete the circuit which withdraws the support for the trapdoor and lets the bad guy’s own weight cause the door to open and thus drop him into that 10 meter pit of which you spoke. Or you could have the thief be dropped into a room full of security guards armed with shock gloves, Stechkin OTs-38’s, and sturmgewehrs along with the usual Police veteran German Shepherd (Fritz, KILL!).

    • Hmm. Untouchables.

      Cue pre-Miranda rights “puir beat cop” Sean Connery with Ithaca Auto & Burglar from out the gramophone:

      “Isn’t that just like a ***! [Insert ethnic slur/pejorative du jour here] Brings a knife to a gun fight!” “Get outta here ya dirty **** bastidge!” Knife wielding assailant turns, runs.

      Cue hideous if well-dressed Mafia button man with Thompson: “Ratatatatatatatatatatat!”

    • My ideas seem to run on Prohibition Era Logic (incidentally, the patents for trapdoor defense were made at that time if I’m not mistaken)… And yes bank tellers today would probably love to have trapdoors of doom installed to thwart robbers. The Police would make sure NOBODY said a thing about banks and small shops having trapdoors installed…

      • I can think of places like post offices and doctor’s reception desks, where having the trapdoor trigger button on the customer side of the desk might work wonders for customer service…

          • Unfortunately the failings of state sector monopolies and cartels (NHS doctors fall into the latter category), are universal

            They depend upon the lack of competition for customer’s money. Rather than on place.

            The postal disservice in the united state is as bad or worse than the British one.

            Once in a while, private sector competitors do spring up, and are very welcome. Lysander Spooner famously set up a rival to the united state postal disservice, and was forced to close it, following threats of state sector violence.

            As Rothbard observed, monopoly can only exist through violent coercion. It cannot survive on an unhampered market.

  14. Absolutely marvellous coverage of this Ian! It is wonderful to see this amount of disassembly of something so famous yet obscure. I had read of this gun and the Webley-Fosbery style indexing but it was so much more exotic than I had imagined. The flow forward system certainly is a bit exotic too but the op-rod containing part of the trigger mechanism is the strangest thing I think I have ever seen in gun design!
    Just a thought on the shell extending into the barrel slightly. I am guessing that only occurs within the recessed front face of the cylinder rather than beyond it. Otherwise the longer fired shell would potentially impede rotation.

    • Actually that was a completely different weapon, the CAWS iirc. Basically it was a souped up bullpup conventional semi/full auto shotgun designed to use high pressure AP (tungsten pellet) all metal shot shells.

    • I quite like the G11’s vertical rotating chamber thing, if I remember correctly… You could hold alot of shotgun cartridges stacked vertically in a line along the top, inconjuction with a similar operating system to the Jackhammer blow forward etc, you could get the gas seal thing might be quite good.

      • Obviously that used caseless ammo, so you’d need to sort a method of ejection out… Gas should blow the empty out, the barrel moving forward could lift the “bolt/back plate” clear, prior to this movement rotating the chamber for reloading, rotating it back on it’s return timing is important etc.

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