Hill SMG/Pistol: Inspiration for the FN P90

John L. Hill was a World War One fighter pilot who went into the oil and gas industry, and enjoyed tinkering with guns in his free time. In 1949 he got an idea for a new style of magazine and feed system, which he developed and patented in the early 1950s. Hill’s intention was to create a submachine gun for the military or police that held its magazine flat atop the action, instead of sticking out of the gun where it would get in the way. To do this, Hill designed the system that would be later used in the FN P90, with ammunition held perpendicular to the barrel, and a turret mechanism in the action to turn the cartridges 90 degrees for feeding in the chamber.

Hill built 7 or 8 fully automatic prototypes, which were examined by the US Army and the FBI. One was tested at Aberdeen Proving Grounds in 1953, and we still have some of the photos from that examination (that particular gun was guilt using an MP40 barrel, interestingly). Hill’s guns varied in pretty much all details, including different barrel lengths, stock configurations, and magazines. Some used single stack and some double stack magazines, but all were a simple blowback action.

At some point in the late 50s or early 60s, Hill sold his patent rights to a pair of Texas businessmen who built 90 or 100 more examples (mostly semiautomatic) under the name H&B Enterprises. They took one to FN in Belgium, who found it interesting but did not opt to license or produce it. Ultimately, nobody was interested enough to put the gun into production, and only a small number of the H&B guns survive today. The original Hill prototypes were donated to the Lone Star Flight Museum in Texas in 1993, although it is not clear where they are today.

When FN began to design the P90 in the early 1980s, Hill’s concept made a return. It is not known exactly how much direct link there was between the Hill prototype and the P90 concept, but the eventual patents filed on the P90 do reference Hill’s patents (among others). The P90 remains the only production firearm to use this clever rotary feeding system.

Hill’s patents:

Other documents:
John Hill letters

Hill SMG Appraisals


  1. I’ve never heard of this one . Fascinating…. I wonder how similar the rotation scheme is to the new Keltec that has a similar feed geometry. Thanks for this, Ian.

  2. “although it is not clear where they are today.” I feel a rant coming from a certain mustachioed man!

  3. Did anyone else try to wipe the water droplets off their screen?

    Happily, the KelTec P50 will soon be in production to soak up some of the excess P90 mags on the market since the demise of the AR57 upper.

    The late lamented AR57 upper was my choice for the Lyndon, briefly the easiest to build semi-auto centerfire rifle one could build from parts, consisting of nothing but the AR57 upper, an AR-15 trigger jig, and an AR thumbhole stock.

  4. Ian good day, Plainfield Machine Co. NJ, built Qty of Bill Submachineguns in the late 60s both in 9mm and .380 which I tested there and have the original Catalogues printed by Plainfield Machine Co. There was a great interest in Southamerican MODs for the Hull SMG in 9mm and could not understand why Rick Richmond didnt quote them when he received the Official RFQ delivered to him personally, after he received importando orders for PMC M1 and M2 .30 Carbines. Regards, Fernan A. Febres (Latinamerica).

  5. Growing up next door, in Fanwood NJ, my first firearm wsa a PMC M1 carbibe that my uncle gave me as a present (my Uncle Arthur wsa the hunter, Umcle Al was the fisherman – somertimes they even rented a cabin on a lake together and I got to join thir sons in the party) for my eighteenth birthday.

    A very good history of PMC – including their involvement with Hill


  6. 1. First, I do know how ro spell, so ignore the mispellings

    2. Frankly, I fail to see the advantage of this sistem over say, an Uzi. It seems needlessly complicated – think “expensive” and subject to failure – compared with plain blowback. Remember the Puteaux machinegun, which was designed to avoid the Hotchkiss patents and featured a gas piston that got blown forward and requited &diert knowns amount of jiggery-pokery to with the bolt backwards and foeward like everyone else. With the beginning of the Kaiser War, the French learned their lesson and stripped their North African garrisons of Hotchkiss guns and gave them Puteauxs to hold off the Rifs from Fort Zinderneuf until such time as some Hotchkiss guns could be spared from the Western Front

    3. The late Fifties was a horrible time to try io introduce a new SMG – the world was awash with surplus weapons from WW2 and the assault rifle (which has largely replaced the SMG) was on the horizon. I think the US Army verdict was, “Interesting, but what does it do that the M3A1 doesn’t do and, by the way, our brand new M14 is going to eliminate SMG’s in the US Army”. Ian Hogg reported a conversationn he had with an arms dealer who said whenevr somebody had an idea for a new SMG, he took them on a tour of his warehouse to see thousands of unsold SMG’s

    4. Since this was a weapon intended for military use, the ability to fire any but full metal jackrted ammunition would have been irrelevant. In the opinion of the Judge Advocate General, ammunition such as wad cutters and hollow points was (and is) illegal under the Laws of Landwarfare (the bit about “causing unnecessary suffering”)

    • Col,
      I agree with your Point 2. about the Hill, but I’ve come around on the FN. I was very skeptical initially of the 90deg cartridge “gymnastics”, but FN’s simple solution has earned a very high reputation for reliability.

      They also improved considerably on Hill’s idea by reversing the feed direction. The ability to carry 50rds without significantly increasing the size of the weapon, plus bullpup-friendly downward ejection, are definite advantages. It’s just a shame no one has done it for any other cartridge.

      • The stroke of genius of Rene Predazer (FN designer) was making the cartridges rotate simply because of the geometry without any mechanism.

        • Genius indeed! Two nonmoving, self-lubricating polymer inserts, the essence of elegance. I’d love to see the same brilliance applied for 10mm.

    • “The late Fifties was a horrible time to try io introduce a new SMG”
      Worse yet – it was not only new but also own magazines, rather without chance to adopt to existing magazines, so without ability to leverage “we can make it using your magazines”

  7. There was an excellent article about the Hill design in Small Arms Review. A number of the prototype submachine guns still exist. IIRC the article mentioned doing range tests. You really should research the subject and see if you can contact the owner(s). Of course, they may well contact you after seeing this.

    The SAR article stated that Hill was in Denver scouting oil properties, but was snowed in for a while. So he built his prototypes in a closet machine shop.

    • I forget about the guy who wrote the article itself, but I know Herman has passed away since then. The gun itself was auctioned from Herman’s estate and is how I got it. A big reason why I sent this gun in to Ian was there was so little I knew on it, though I figure that I would be able to learn a lot more if this was sent to him. I didn’t know anything at all about the semi auto ones like mine for instance.

    • “There was an excellent article about the Hill design in Small Arms Review.” – Is this it: Bob Pilgrim: The Hill 15 Submachine Gun (Small Arms Review March 2004) [https://www.smallarmsreview.com/display.article.cfm?idarticles=2060]?

  8. Dear Beausarbe,
    The primary advantage of laying the magazine parallel to the barrel is that it reduces the silhouette of the gun, especially when it is used as a personal defense weapon by truck drivers, sappers, signalers, etc. That allows support personnel to carry their SMGs in belt holsters, leaving their hands free for their primary duties (e.g. signaling).
    Note that some more conventional SMGs (e.g. Hotchkiss) could fold their magazines to stow under the barrel and parallel with it.
    When I was a tanker, we thought that the 30 round magazine sticking out the side of a Sterling SMG was a nuisance. Protruding magazines often hang up on seat-belts, door handles, parachute suspension lines, etc.
    Later, when I became an air force technician, we were forbidden to carry weapons on top of CF-18 fighters. We had to leave our SMGs at the bottom of the ladder for fear that they might punch holes in the frightfully expensive composite skins.

  9. Dear Ian: A very interesting article regarding the “Hill”. As you have a penchant
    for gun design technology, It would be very interesting to have a description and
    a comparison with the canadian ROSCISZEWSKI design. Gratefully.

  10. Very cool design! But… does the magazine feed spring push the cartridge into the slot of the turntable or is it gravity fed? If the latter, that could be a problem like with the guy hanging upside down from a building in the picture.

  11. This is the funny (or sad if you wish) part with firearms design, especially when designer was self-motivated. It almost never finds application. And on top of it he faces legal challenges.

    If one works as a part of established firm, sales/marketing gives him a specification and he fulfills it; in many cases it ends with a product.

  12. The magazine is the only thing that has good things to say about the P90.

    For any automatic weapon, the feeding system is paramount.
    And by creating a potentially fail-safe system, Hill took a big step.
    Even if he himself did not have time to figure out exactly where.

  13. Dear Ian,
    When are you going to review Holek’s ZB47 and CZ246 SMGs? We are especially curious about their feed mechanisms.

  14. Those photos look like an mp40 barrel… There was a twin mag mp40 or 38, forget… Wonder if you could run these vertically I.e. Two mags but with the bullets facing down, one mag either side of the barrel. A sort double stack single feed arrangement, er… But not just the mag, or not the mags… Instead/or/and two cartridge holders on a “turny” thing, that pivots… One barrel… Sort of bounces between either mag, one shot one mag, next shot other type thing… Twin mag mp40 idea but, diffrent.

    Anyway I never knew about this Hill rifle either, so it is very cool.

    • Or bullets facing up… Rotary “turny” thing, clearly… But it goes, from right to left also; left mag, left cartridge holder in “turny” thing. To fire it rotates, to barrel, thus right cartridge holder in “turny” thing is aligned with right mag. Fires, entire turny thing “yes” moves left, so left cartridge holder is aligned with left mag, and the right is now inline with barrel… Repeat.

      • Might not work, but it did just come to me; via the mp40 barrel on photo and thinking about the mag switch version of said gun.

        • Bump stock; knock rounds into cartridge holders “turny” things, while rotating it… Aye it would work upside down, if in thevp shoulder etc he he, meh ways… Kind of Gast gun, but with one barrel… Turning circle is less than the movement of a bolt going back an forth per round, it’s half given zwei mags. With short rounds, he he… Possibly. Meh 24rds… He he.

      • Rather than alternating, I’d prefer a manual selector lever like the KSG’s. That way you could keep standard (HP) ammunition on one side, and specialty ammo (AP, low flash, etc.) in reserve for special circumstances. It would also be simpler mechanically.

          • Although actually, you might have to then have two “turny” things… Running on one bar… That each pivot independently via a switch… Your making this more complicated than the Gast gun in principle idea… Laws is it, he he. We won’t be saying that if the Kasier attempts to “pump” us all.

            1917… Sales, no… He he.

          • You would actually, it auto feeds from the left mag, to the right in the original config.

          • 24 shots in a package no longer than a 12 round mag…

            Without a giant 24rnd banana mag. Is the selling point, not ammo switching, on this occasion.

          • 12 rounds stacked “opening” end up, or down… Probaly up, but certainly not right or left.

          • A friend had an excellent idea along these lines: twin, side-mounted P90 mags, held in a block that could be toggled left or right.

          • Great, tell em to kel tec it polymer shotgun; home defense, needs marketing, probably he he.

          • We need these things made, so we can scale them up to 30mm etc… If required; Proven designs. Americans like shooting pumpkins with, guns; larger than a gat gun= Proved’ish • R = popped robots. R being robots, he he; meh new to equations.

  15. No it auto feeds, can’t cut one mag off currently, sorry; they’ll be ways, not via a bump stock perhaps he he, fiddle have fun.

    In principle though why not? 2 of these mags “bullets” up etc; either side of the barrel/action.

    • (Not thought this through much; but bump stock = rotate one recoil impulse, return spring rotate again; fires, so on.) Could be multiple problems, but mags that fit thus, could hold more rounds.

      I.e. Length of gun; maybe they fold, disintergrating link… Or such, in a pouch it is 2 mp40 mags together; but to load you extend it. Might be ok for robots a drum of folded ones, it then can extend to feed. Be all kinds of this bollocks in the future you know, they’ll work out all the spots we could attack from and man them with robot & worse probably.

      • I’d like to say it would make war less likely, but I have a bad feeling about the nature of life; if robots, are “better” I think we’ll naturally get smoked. Electric is alive, in away; and really, really we don’t know what life is. Maybe whatever it is, will go for them; our creations.

        Well fuck that, they ain’t getting the T.V “Mars Attacks movie, he he.”

        • & even if you guys disagree, with “robots becoming self aware” never mind that, it will be evolve from human use I.e. The Chinese etc will make A.I ground holding robots anyway as doubtless will we. Against normal troops. But we need to be able to blast them. They might run around a lot… Like a spider, more rounds bigger calibres by more folks is maybe the best option; they might clock an rpg round and move.

          • A “walking” bunker, in essence if that sounds less fanciful, the ww1 machine gun post that moves around a bit; from were they drop it and think your coming, doesn’t need rations or tea.

Leave a Reply

Your email address will not be published.