Hello, my name is Dino Snider and I am designing a new shotgun shell. My motivation for this is as follows. The 'modern' shotgun still carries the baggage of last century's blackpowder legacy. The cartridges are sized to hold old and weak powder, and the guns are still not designed to take advantage of newer smokeless rifle powders, instead being forced to get by with pistol powders. This results in an inability to fully use a rifle or even carbine length barrel, and prevents high velocity payloads. This sorry state of affairs results in low firepower for a shotgun, with firepower being defined as a combination of the individual round's effectiveness combined with the number of rounds carried in the magazine.
In an attempt to rethink the shotgun shell from scratch, I began with a series of design requirements:
1) duplicate or exceed the performance of a 12 gauge, 3 1/2", 14,500psi Magnum shell
2) optimize the round for a payload of 00 buckshot - the standard tactical load
3) optimize the round for high tubular magazine capacity
4) optimize the round for use in a short carbine-style barrel, no longer than 18", maybe even as short as c. 10"
5) base the prototype round on an existing round for simplicity in testing, later for manufacturing.
I believe I have reached an optimal round configuration, based on the above requirements.
The criteria dictated a short, stubby round for efficient powder use, and for a higher mag capacity. The diameter of the round logically had to be some diameter of payload that efficiently stored 00 buckshot well in its cross section. A cross section (sans 'power piston' carrier) of 1" was perfect, since 00 buckshot is .33" diameter. A bit more is allowed for the shot carrier. This allows 7 round of 00 buckshot in cross section. An inch of payload space allows a payload of 20 pellets while allowing plenty of space for the carrier. Alternatively, a .24 cal #4 buck could be used where overpenetration is an issue - this would allow 7 across. This would presumably be nickel plated and buffered chilled lead core, for minimum deformation. The stubby round has the added benefit of burning a full load of powder quickly and reliably, allowing for no 'muzzle flash' with a carbine length barrel, and also results in an accurate payload delivered to the target. This stubby round closely resembles the efficient .308x1.5" Barnes silhouette cartridge in this respect.
The choice of existing rounds was a long and difficult process. The author of 'Rapid Fire', Mr. A. G. Williams, has been an indispensable help in the research. I chose the 30mm x 113mm belted round, the round used with the HE shells used in the Apache gunship. The straight wall and belt makes home testing easier. The round can handle high pressures - about 45,000psi - a very real issue with the Barnes style cartridge shape (the shell is rated for about 40 - 45,000 psi in normal use). Compare that to not much more than 10,000 for a typical shotgun.
NEWS UPDATE: I found modern brass! The new US rules mean I had to look elsewhere to order some. The round is normally electrically ignited. A militaria dealer on the web volunteered that the M36 percussion primer is compatible with the 30mm round - what luck! I want the British brass based round since I don't know much about the behavior of alloy or steel shells.
If things go well, I'll have a round capable of c 3000 fpe. I want to use light, fast loads to keep recoil down, plus to make full use of the rather small payload space available. I'm not sure if I can keep the round length down to 2" without pushing the envelope on powder types and maximum presssures. I'm going to try, though, since this makes the overall firepower of such a shotgun higher. A standard tactical shotgun should be able to hold, um, 10 or so of these rounds. By intelligent use of fin stabilized slugs (I'm toying with a manufacturing process on this), or just plain old two metal mass slugs, a single mag of this stuff should be able to send enough lead downrange to match a mag of standard assault rifle fire. I just built some mass slugs by tacking a .22 bullet onto a rimfire case. A spitzer load like this would do real damage with a MV of 1500-2000fps. I am interested in finding out whether the Calico-style helical mag could be adapted to feed from where the tube mag usually goes, or it could be mounted front and top. (Yes I have a patentable variant in mind.)
Hey Hollywood, you thought the Desert Eagle was distinctive? Check this out!