Weird Magazines, Vol. I: The Kottas Magazine System

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The truly high capacity magazine has been a dream that firearms inventors throughout the world and time have endlessly pursued. One of the crazier attempts to improve the capacity of the Steyr-Hahn 1912 handgun was a system designed by Arthur Kottas. Over at Historical Firearms, Matt elaborates about this unusual and eyebrow-raising magazine design:

The patent drawing above shows an unusual magazine system developed by the retired Austrian army officerArthur Kottas. Kottas’ magazine combines a looped channel within the stock with a horizontal feed which turned cartridges as they entered the action to be chambered. Kottas first patented his design in Austria in August 1918, before the end of the war, and later patenting it in the US in 1921.

The pistol Kottas uses to demonstrate his magazine design is a Steyr M1912 semi-automatic pistol, itself designed by Karel Krnka. The conventional M1912 was loaded with stripper clips into an 8-round box magazine in the pistol’s grip. The M1912 was a robust and reliable early pistol design and ran well in the field, its stripper clip feed system being its primary drawback.  

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Steyr M1912 with an 8-round stripper clip (source)

While a fully-automatic capable variant of the M1912 with an extended 16-round magazine was developed Kottas’system would have potentially offered capacity for approximately 60 rounds. Kottas’ magazine system is complex and convoluted using a steel band to pull cartridges through the magazine into the pistol’s action.

From Kottas’ patent it is difficult to ascertain exactly how the system works however, from the patent’s explanation we learn that the ammunition is loaded in the usual manner with a stripper clip from the top of the receiver where a ‘turning member’ then turns the cartridges 90 degrees and into what Kottas called a ‘loop’ (a single stack quadrangular channeled magazine) aligned transversely and as the weapon fired the ammunition was turned by a pair of spiralled feed lips (see fig.2 & 3 on the patent drawing) as they entered the action aligning it with the breech. Rather than a follower and magazine spring Kottas employed a wound ratchet system that pulled a steel ‘conveyor’ band which ran the length of the loop and pulled cartridges towards the action. The conveyor band had four dummy cartridges at the end which acted as a follower (seen in the grip in the patent drawings) these were also intended to act as a slide hold open device.

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Kottas’ patent drawing of his system’s magazine ‘loop’ (source)

The diagram above shows a cross-section of the butt of Kottas’ design showing a ratchet device attached to a crank to pull the cartridge conveyor back along the channel and apply tension to the steel loop. The patent and drawings are unclear on just how the action then pulls the conveyor band back through the magazine to feed the ammunition up into the action. It explains that the second disc at the base of the stock’s grip is is attached by a pawl to the pistol’s slide. During firing when the slide reciprocates the pawl is actuated pushing the cog-like wheel which in turn acts upon a coil spring to maintain the tension on the loop pulling cartridges up to the action. Another interesting feature was that the conveyor band was numbered to indicate how many rounds were left in the magazine. This could apparently be read as the conveyor passed through the crank at the top of the stock.

Somewhat surprisingly, Kottas’ patent has been referenced several times by major firearms manufacturers patenting ideas in the same vein. Colt, Fabrique Nationale, and Taurus all reference the Kottas patent, but also John Hill who designed a transverse magazine that we’ll take a look at later, and even United Shoe Machinery Corp, who referenced it for a magazine designed for the AN/M2 machine gun.



Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He can be reached via email at nathaniel.f@staff.thefirearmblog.com.


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  • Craig MacMillan

    luger had the 32 round snail drums

    • Anonymoose

      If you want to get more recent, They make C-Mags for the 9mm Glock, and Promag used to make that “trashcan lid” drum for the 1911 (which from all accounts was a colossal POS).

  • Jean Luc Picard

    There is many “weird” setups in firearms.
    P90, Snail Drums like mentioned bellow, Treeby Chaingun, Evans Rifle with it’s screw cylinder mag, the calico, gycot chain Rifle, the hill submachine gun, the Dardick Revolver, O’Dwyer VLE Pistol, Meigs 50 shot repeater, spanish 25 shot mag for the ascaso pistol.
    I think we can make an entire subject about that 🙂

  • ostiariusalpha

    One simple problem with this design as it is layed out in the patent drawings – the rounds are still perpendicular in the grip! That would make it enormously fat in 9mm Steyr, and even with the shorter 9mm Luger it wouldn’t be very ergonomic to hold. If they’d ever gotten around to making a prototype it would have become obvious that they need to move the transition below the grip, but then the follower wouldn’t be able to push the last few rounds. The only solution I can think of is to drop the idea of having the magazine feed up through the grip at all, and just separate the two like a C96 or even put it behind the grip.

    • AMX

      The follower already has four rotating dummy rounds on it – just add a few more.
      Pretty sure you could do it with 8 (the capacity of the normal Steyr-Hahn) or less, so we’re still talking about a capacity of 52 or more.

      • ostiariusalpha

        From the schematic, you’d need at least 10 dummy rounds to maintain the bolt hold function and have the “turning member” at the bottom of the grip. That many rotating dummies would develop real friction problems inside the magazine.

        • AMX

          Can you elaborate on that?
          I don’t see why dummies would produce significantly more friction than the live rounds they replace?

          • ostiariusalpha

            Live rounds are free to roll in the magazine, it reduces friction greatly; the dummy rounds are just going to slide against the walls of the magazine. It’s not a problem for 4 dummies, but 10 starts to need more effort than the powder charge of the round can supply and you get reliability problems.

            This is what the cartridges are actually doing inside a single-stack magazine, and why they have reduced friction:

          • AMX

            Thanks, that makes sense.
            Should be possible to deal with, if we connect them using articulated links – but that’d be pretty fiddly.

          • ostiariusalpha

            Yeah, that would take it over the edge into full-on Rube Goldberg boondoggle contraption territory. It’d really be much simpler to separate the grip and mag.

          • AMX

            i just realized that we’re debating a nonissue – this isn’t actually a handgun anymore, it’s a pistol-calibre carbine.
            Plenty of rifles out there with a stock that’s wider than 33mm…

          • Well funny you should mention articulating the dummy rounds, that’s exactly how it works.

          • ostiariusalpha

            AMX means giving the rounds a 2-dimensional articulation (rotation and rolling), whereas the ones in the original drawing only have 1 dimension of articulation (rotation) with the rear most dummy round having rollers but no rotation.

          • ostiariusalpha

            Hmm, maybe. An M1 Garand grip is about 35 mm thick at it the point where your fingers wrap around it, but you’re essentially cradling it between both of your hands, one one the forend & the other on the grip, to press it against your shoulder. Other stocks that have even thicker grips are more for resting your hand on than wrapping your fingers around. The difficulty is that machine pistols like this Kottas design don’t have the right angle on the grip to use it like you would a fat rifle semi-grip, it puts your trigger finger in a really bad position for leverage if a vertical grip is too thick at the web of your hand. Weapons designed for offhand point shooting like machine pistols favor thinner grips that you can wrap fingers around. Also remember to include the space inside the mag for the round, the metal walls of the magazine, and the woodstock the mag is housed in for the overall thickness of the grip; that puts the 9mm Steyr at an absurdly unusable thickness, and even 9mm Luger would be pretty poor ergos like I said before.

  • Kivaari

    This isn’t about this. I was lucky to handle and shoot the Greer MFG (Mollola, OR.) .22-45 conversion kit. It comes with a special magazine having the ejector on the magazine. One can convert a 1911 to 22 by changing just the barrel and magazine. It has a clever offset bore. It’s been on the latest patents list for the 1911. I’m surprised it hasn’t been picked up by a big gun company.

  • Fruitbat44

    Well, that’s definitely thinking outside of the box . . .