The Special Operations Weapon was a blow-forward operated, select fire shotgun used by US Navy SEALs

United States Navy SEALs

The United States Navy's Sea, Air and Land Teams, commonly known as Navy SEALs, are the U.S. Navy's principal special operations force and a part of the Naval Special Warfare Command as well as the maritime component of the United States Special Operations Command.The acronym is derived from their...

 in the Vietnam War

Vietnam War

The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...

. It was designed by Carroll Childers, an engineer at the Naval Special Weapons Center. The 870 mod kit provided SEAL shotgunners with a quick-change magazine holding 20 rounds. The SOW was full-auto.

Combat scatterguns

The meat-mangling effect of a scattergun loaded with buckshot is no secret. The 12-gauge pump action repeater has been in U.S. military service since clearing trenches became a necessity in World War I. Marine combat experience in the jungles of World War II unmistakably proved the utility of the military shotgun for close-range encounters where silence is not the primary factor. It was not long after the first Navy SEALs deployed to Vietnam that this lesson was re-learned. The Ithaca Model 37 was a standard issue shotgun in the Navy in the 1960s, used mostly by boarding parties and for inport ship security. When the newly commissioned SEAL Teams got a bunch of the guns, one of the first things they did was to strip off the visually impressive, but practically useless, barrel shroud and bayonet lug. This resulted in a handy, four-plus-one slide-action 12 gauge, weighing merely 6.4 lbs. and measuring just under 40 inches, a particularly efficient package. The downward ejection of the gun gave it a further advantage over competing designs. With no ejection port on the side to serve as a second entry point for the ever-present crud, rain and mud, it was particularly resistant to jamming. Just as their many predecessors had discovered, the SEALs found the awe-inspiring roar of a 12-gauge shotgun in the hands of a well-trained pointman to be just the ticket when ambushed. Much practice was devoted to the technique of furiously pumping the slide mechanism for ultra-fast return fire in the critical first seconds. But, there is always room for improvement, and gun’s limited ammo capacity was one obvious candidate. The Navy’s China Lake gun gurus went to work, and by the end of 1967 began shipping over a modification kit that extended the gun’s tubular magazine to hold three more rounds. This gave the Model 37 a grand total of eight on board.

Box magazines

Still, the Ithaca’s underbarrel tubular magazine took far too long to reload when things were hot and heavy. A detachable magazine made sense, and early in 1970, according to Thomas Swearengen in his essential reference book The World’s Fighting Shotguns, Navy firearms engineer Carroll Childers put his considerable talents to this task at the Naval Surface Weapons Center. A prominent Science Advisor who spent several months in the war zone in 1968 and again in 1969 as part of what is sometimes called the Vietnam Laboratory Assistance Program, Childers had already provided the SEALs with a reliable 50-round magazine for their M16 rifles. Building on this successful innovation, he soon produced a pair of cleverly designed aluminum boxes reliably feeding 10 or 20 rounds, staggered in two rows for compactness. This was no small feat with the big, heavy, fully rimmed shells that jostled around under the punishing recoil of 12-gauge loads. Since the Navy’s standard issue Ithaca loaded and ejected from the same hole under the receiver, this gun was not the ideal candidate for conversion to magazine feed. Fortunately, the Remington 870 was mechanically suited, already in the Marine Corps inventory, and well liked by Force Recon units that sometimes operated with SEALs. Childers and his team produced a fairly simple and easily applied modification kit for the 870 that performed well in testing and was all set for production when the word came down that the U.S. was pulling out of Vietnam.

Pellets and chokes

Another characteristic needing improvement was in patterning, the distribution of multiple lead balls at varying distances from the muzzle. There are at least two main components to this—pellets and chokes—and the ideal combination sparks a never-ending debate among shotgunners. While the big double-ought round with its nine .33 caliber balls remains even today a combat-proven military standard, it is noted in contemporary accounts that most SEAL shotgunners preferred smaller #4 buckshot. Perhaps puzzling to the casual student of wound ballistics, this should not be hard to understand when properly considered. Although the projectiles in the #4 round are only .24 caliber, their combined weight in the shell is the same as that of the nine pellet 00 buckshot, and there are 27 of them flying though the air instead of nine. Keeping in mind that the incapacitating effect of gunshots increases markedly with multiple hits, the #4 shot is still large and heavy enough so that relatively few need to find the mark to cause sufficient damage to immobilize or kill. This plethora of flying lead would be of only marginal utility if not efficiently delivered to the central mass of a man-sized target at realistic combat ranges, and this is where chokes come in. Any number of chokes—most simply defined as muzzle diameter restrictors—have been developed over the decades for sporting and military applications. But the SEALs wanted something quite different. Give us something, they asked, that will increase hit probability and thus pointman survival in a close-range jungle ambush. Initial experiments at Frankford Arsenal in the mid-1960s pointed to ordnance engineer Charles Greenwood’s duckbill choke as a promising avenue for further development. When properly oriented on the muzzle, this V-shaped device restricts the top and bottom of the shot pattern so that a larger number of pellets fly in a horizontal plane, increasing hit probability against closely grouped enemies or those running parallel to the gunner. However, SEAL combat experience with duckbill-equipped Model 37s and carefully observed formal testing would eventually demonstrate that the concept was not as practical as hoped except at relatively close range. According to Swearengen, controlled tests showed the duckbill would consistently put only a few pellets from a #4 shot anywhere in a man-sized target placed 40 meters away. In contrast, a traditional cylinder choke could be counted on to deliver on target at least 60 percent of the balls; that is 16 hits per shot. This pattern density is all the more crucial when shooting through dense jungle vegetation, and the duckbill’s popularity faded away along with its novelty value.

Full auto follies

As good as the Model 37 became—and the box magazine–modified 870 could have been—the ageless concept of “more is better” spurred other areas of experimentation with a series of noteworthy developments in rapid-fire shot throwers. The Remington 7188, first to be fielded by the SEALs, was a full-auto jackhammer based on this great American gunmaker’s respected Model 1100 semiauto hunting gun. Although boasting a cyclic rate of about seven rounds per second, the gas-operated 7188 reportedly was difficult to control as well as prone to malfunction from environmental factors. Meanwhile, back at the Naval Surface Warfare Center in Dahlgren, Va., magazine master, gun enthusiast and engineer Carroll Childers had been hard at work on a completely different full-auto shotgun. Colorfully acronymed SOW for Special Operations Weapon, it was to be no mere conversion of an existing gun. Childers knew he had to come up with something completely different to meet the demanding standards of Marine Force Recon and Navy SEALs. Most importantly, the gun would have to be a light and compact package that would reliably feed and controllably fire not only various military standard 12-gauge shells, but also to launch a new family of special-purpose munitions. Although of the same caliber, these SPMs had necessarily longer cases and widely varying recoil impulses. A developmental SOW—called at the time the MIWS for Multipurpose Individual Weapon System—is preserved among many other one-of-a-kind artifacts in the Naval Historical Center’s collection. The chunky and stubby slab-sided aluminum and steel first-generation prototype is fed from the top using one of the multi-round box mags Childers developed for the 870 shotgun. This one is apparently intended for hip fire only, featuring two pistol grips with heavily worn and deeply scratched olive drab paint giving much evidence of rough use during its short, but fascinating life as a test subject. Development of the Childers SOW and its remarkable family of 12-gauge ammo had come tantalizingly close to warranting a full-scale program when the Pentagon pulled the plug on small arms research and development.

External links

• "Firearms secret projects" thread at Secret Projects Forum