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The DuckBill Choke From Great Lakes Arsenal

By Jeff W. Zimba

Move over chainsaw, here comes the DuckBill.

The first time I actually saw a photo of the mysterious Duckbill choke I used to hear about once in a while, was in the book Special Warfare, Special Weapons by Kevin Dockery. It was designed by the U.S. Navy in 1968 to change the pattern of the shot from circular to a horizontal oval, and was fixed to an Ithaca model 37. It was adopted by the UDT/SEALs for use in Vietnam. While I was intrigued by the idea of a choke that spread shot from a shotgun to a 4:1 ratio horizontal pattern, it was not available any more, and it did look kind of funny anyway.

A few years went by, and one day while browsing some gun pages on the World Wide Web I saw it mentioned again. This posting was by a fellow named Chuck Madurski from Great Lakes Arsenal, Inc. and it stated that his company was going to go into production on a new and improved shotgun choke based on the original Duckbill design. It took only seconds before my fingers started typing an e-mail to Chuck to obtain whatever information I could. He confirmed that they were going into production, and I was welcomed to test one of their units for Small Arms Review should I desire. I gave him the shipping information and the wait was on. A few days later, a Remington 870 barrel with a DuckBill Choke showed up at my door.

It is designed a lot like the original first model duckbill as far as appearance, but the new unit has been improved in strength. Where the original was manufactured from low carbon steel for ease of manufacture, the Great Lakes Arsenal design uses 01 oil hardening drill rod. The U.S. Navy facility at China Lake that manufactured the originals gave the duckbill choke its characteristic wedge shaped cut by using a side-milling cutter. This led to stress cracks at the bottom radius causing the unit to slowly open up under heavy use. Great Lakes Arsenal has solved this problem by making their cuts with a modern wire-EDM machine.

When it first arrived, I was knee deep in deadlines and it stood up, leaning against the wall in my office for some time. Everyone who saw it thought it was something different. I entertained all kinds of guesses, from some type of tool, to an entry / breeching round adapter, to a grenade launching adapter. After a short explanation and condensed history lesson, everyone who saw it was intrigued. The real intense interest came at the range.

I stopped at a 50 yard pistol range, pulled the gun out of the case and set it on the trunk of my car. I proceeded downrange to lay out some cardboard. Everyone walking by the shotgun looked at it funny and said something similar to “what to hell is that?” We first tried a couple rounds of #6 lead shot from a distance of 20 yards or so and walked up to the cardboard. Everyone’s jaw kind of dropped a little while we all muttered “holy sh*t. This thing really does exactly what it is supposed to do.” The pattern, with all shot, from #7 bird shot all the way to 000Buck, was compressed to a horizontal pattern of at least a 4:1 ratio. We found that if fired once holding it horizontally, and then once with the same point of aim, but held on it’s side, the shot pattern would be of a perfect “X”.

My Remington 870 still looked like a shotgun, but was behaving more like a chainsaw. As a matter of fact, I was shooting the test patterns on a piece of 3’x4’ cardboard leaned up against a little 2x2 to avoid any shot deflection problems. After firing less than 20 rounds at distances varying from 10 yards to 30 yards, the little 2x2 was almost ripped in half in the center, with barely a visible blemish a foot or two above or below center. Pretty impressive. Everyone who witnessed this choke in action immediately asked “How much?”
For applications other than tactical ones, in the author’s opinion it would make a great hunting aide if you hunt with buckshot. Just imaging leveling on a Whitetail Deer and having the ability to hit it from nose to tail while placing the vast majority of the shot in the body area. Depending upon the distance, you may end up with no shot being thrown over the back or under the belly. That really gives the hunter an enormous advantage when a running lead is necessary on a moving target as well. This really creates a serious wall of shot. As for competition, just imaging how long it will take to clear a table of bowling pins with this device. I give it about 2 weeks before it is disallowed by competition governing bodies.

One odd thing noticed by all was the tendency for the unit to act as a tuning fork when the action is racked. A quick cycling of the action is always accompanied by a high pitched ringing. This is really no big deal, as any member of an entry team would have a round chambered before entry, therefore eliminating any audio detection risk. As for hunters, the same would probably apply. This is an easy fix if it is still a concern though. After looking it over for a minute, a friend asked me for an elastic band. A few wraps around the end and no more ringing. It should be sliced with the first shot and disappear from sight. In mentioning this to Kevin Dockery, he said it could also be solved by placing 1/2 of a camera film canister over the end, if it was really a factor for anyone, and that it would also keep any vegetation from being caught in the DuckBill design.

These units are permanently attached by silver solder to the shotgun barrel and are installed directly by Great Lakes Arsenal. They were designed for #4 buck being the optimum load and are for use with lead shot only. (No slugs). Great Lakes Arsenal will mount one of their DuckBill Chokes on your barrel for $125.00 + $5.00 S&H and this includes your barrel being refinished with a matte blue. The mountings can be done on any non-ribbed shotgun barrel, rather it is a pump, lever, single-shot or even semi-automatic as long as it does not have a reciprocating barrel. The massive shot restriction actually dampens the recoil and would cause a reciprocating barrel semi-automatic to short stroke. They will install one of these units on your AOW or SBS short barrel, but you must provide them with a copy of your BATF Form 1, 2, 3, or 4. They will not cut any barrel below 18.5” but will be pleased to crown your existing short barrel. If you have a borderline barrel, or one cut “a little” short, this choke can make the barrel usable again as it adds approximately 1.5” to the overall length.

Great Lakes Arsenal only needs your barrel, rather than having you send the whole gun. This greatly reduces paperwork and turn around time.

Great Lakes Arsenal
60233 Northern Ave.
Ray, MI 48096-3914

Special Warfare, Special Weapons
The Arms and Equipment of the UDT and SEALS
By Kevin Dockery
ISBN 1-883476-00-3
Published by
The Emperor’s Press
5744 W. Irving Park Rd.
Chicago, IL 60634


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