Skip to main content

The Powerful USAS-12 Full-Auto Shotgun

Did Daewoo make the scattergun even more deadly?

The Powerful USAS-12 Full-Auto Shotgun

Thompson firing a three-shot burst from a select fire USAS-12; note muzzle climb is not excessive. 

Ever since I bought a much-used Model 97 Trench Gun shortly after graduating from college I’ve been enamored of the combat shotgun. I’ve used excellent pump actions, especially the Remington 870 Tactical Models and the Mossberg 590A1. Although I’ve used various self-loading combat shotguns, the Remington 11-87 Police and the Benelli M3 have remained my favorites. Remington enhanced by Scattergun Technologies or, in the day, Robar have proven excellent. I keep both a Remington 870 Tactical and an 11-87 Police, both mounting lights, secure but ready at hand in my residence. As I live in a suburb of a city that often ranks as the most dangerous in the USA, I feel something more than a handgun is justified for home defense, but because of the nearness of other homes, a shotgun loaded with #4 buckshot is more prudent in most situations than an AR-15.

Thompson has normally been satisfied with pump or semi- auto combat shotguns such as this Remington 870.

I have tried various other flavors of combat shotguns. For example, I have done quite a bit of shooting with the Franchi SPAS-12, but though it looks great on screen, I find it heavy and unwieldy. Still, I used to shoot one every few months to stay familiar with its manual of arms, as I did have contact with some European units that used it. The SPAS-12 is a dual action shotgun, meaning that it can function as either a pump action or self-loading shotgun. There is a misconception among some that this was because self-loading shotguns were unreliable in the past, thus it was necessary to have a back-up action.

Actually, the various Italian dual-action shotguns were developed so military or LE agencies could have a semi-auto combat shotgun that could also function with less lethal rounds using the pump action. I consider the Benelli M3 the best of the dual action shotguns. The ability to do a quick reload of a shotgun using a detachable magazine seems appealing; hence, the interest of many shooters in the Saiga-12 shotguns from Russia. I found that feature appealing, but I also found that the protruding magazine tended to snag when doing room clearing drills or moving through any kind of undergrowth. Maybe I’m just clumsy, but that was a negative of the Saiga-12 for me.

The SPAS-12 shotgun is often seen in films because of its “high- speed” appearance, but it is not a practical combat shotgun.

There is another type of combat shotgun not normally considered for civilian self-defense or law enforcement in most countries. I refer to the select-fire shotgun developed for military usage. I first got interested in this type of shotgun when doing research for my book US Combat Shotguns in the Osprey WEAPON series. In Chief James Watson’s excellent book Point Man, about his service with the SEALs in Vietnam, he discusses the Remington M7188 full-auto shotgun developed for the SEALs in some detail. The 7188 was based on the Remington M1100. There was also a semi-auto version, the 7180. As befits a military shotgun, it shared features with the iconic Trench Guns of WWI and WWII. These included a 20-inch barrel, ventilated handguard with bayonet lug (for an M7 bayonet), rifle sights, extended magazine tube, sling swivels, and a sandblasted phosphate finish. As issued to SEALs, it was designated the M7188 MK I. A few were issued to the SEALs who found them very hard to control when firing on full auto. Most preferred their Ithaca 37s, often with Duck Bill chokes. As the 37 lacked a trigger disconnect, by holding the trigger back, the SEAL could fire it as quickly as he could work the slide action.

The USAS-12 (top) is actually a full-auto shotgun that works and is reasonably controllable. The example shown is a semi-auto version, which is still clas- sified as a “Destructive Device.” (Courtesy of Rock Island Auction Service). Right side view of a USAS-12 (bottom); note the channel for the cocking handle if placed on the right side. (Courtesy of Morphy Auction Service)

There have been other attempts to develop a viable full-auto or select-fire combat shotgun. One of the best known is the “The Atchisson Full-Automatic Assault Shotgun.” To cut the cost of development, the Atchisson used some components from the M16. Its 20-round rotary drum magazine gave it substantial firepower. The trigger system was based on the classic BAR (Browning Automatic Rifle), chosen because its buffered sear carrier helped dampen recoil. A prototype was ready in 1972 and seemed promising. The design evolved into the AA-12 (Auto Assault-12), which influenced development of later full auto shotguns, including the subject of this article, the USAS-12 Combat Shotgun. The AA-12 was evaluated by the USMC in 2004 but not adopted. Dual AA-12s were also mounted in the turret of the prototype HAMMER “unmanned defense system.”

Daewoo manufactured an array of weapons, including the K2 assault rifle. The Daewoo K1 assault rifle was intended for ROK special operations units.

Also developed during the 1970s was the “Foote Selective Fire Machine-Shotgun.” Daniel J. Gordon, an Australian, designed the “Gordon Close-Support Weapons System.” Gordon had served with an Australian unit during the Vietnam War and been impressed by the effectiveness of combat shotguns. The resulting weapon was a cross between a combat shotgun and a light machine gun. As conceived, the weapon could be configured to fire rifle ammunition or shotgun shells. The shotgun version was designated the “CWS-1” and was a 12-gauge belt-fed machine gun. During the Vietnam War, the US Navy developed a prototype of its “Special Operations Weapon System” (SOW). The SOW was select-fire and could use a top feed, double stack, 20-round box magazine or a belt. It is noteworthy that all of these select-fire shotgun designs arose during the Vietnam War where meeting engagements were often decided by immediate, close-range, overwhelming firepower. These and other full auto shotgun designs are fascinating, but this article is focused on arguably the most successful one, the USAS-12.

Patent diagram submitted for the USAS-12.

In the late 1980s, the Gilbert Equipment Company developed a select-fire shotgun based on the Atchisson design discussed above. However, as the Gilbert Equipment Company lacked facilities to manufacture the design, Daewoo Precision Industries in South Korea began producing the USAS-12. Some readers will be familiar with Daewoo for the semi-auto versions of their K1 and K2 assault rifles (known as the AC-110C and AR-100) imported before the 1989 “assault weapons” import ban ordered by President H.W. Bush (see Dr. Will Dabbs’ article in this issue). Gilbert Equipment Company brought in the semi-auto USAS-12 shotguns for commercial sales before the ban took effect. However, in 1994 during the Clinton administration, a directive by Secretary of the Treasury Llyod Bentsen went into effect as he directed ATF to declare the USAS-12 a “destructive device” as it was “non-sporting” and had a barrel diameter over a half-an-inch. It now had to be registered using the same process as purchasing any NFA weapon, like a transferable machinegun. This killed all hopes of domestically produced USAS-12 sales, but even if Bentsen would not have done this, the 1994 Brady Bill, with its domestic “assault weapons” ban and “high-capacity” magazine bans, would have killed it anyway. There was also a semi-auto version of the SAS-12 produced during the 1990s by RAMO Defense Company but being a “destructive device” as well as an “assault weapon” during the domestic ban, it could only be produced for government sales.

Close-up of the selector switch for a select-fire USAS-12 (top left). The mag well for the USAS-12 (top right) is tight enough that fitting the drum into place takes care for proper alignment. The ejection port and cocking handle can be changed for either right- or left-hand use.

The USAS-12 found buyers with special military and police units such as Brazil’s GRUMEC, Colombia’s COPES, and South Korea’s 707th Special Mission Battalion among others. Reportedly, more than 30,000 USAS-12 shotguns had been produced by the mid-1990s. According to some sources, Daewoo is still producing the SAS-12 for military and LE orders. The USAS-12 is gas-operated and selective fire. Shotgun shells are fed through either a 10-round box magazine or a 20-round drum magazine. Though a shotgun, the USAS-12 has an “assault rifle” look because of its carry handle and pistol grip. Maximum effective range for the USAS-12 is usually given as 50 meters. It is interesting to examine the patent application for the USAS-12 as it offers an optimistic look at its effectiveness:

The ribbed butt plate helps keep the USAS-12 from climbing on the shoulder during full auto bursts. USAS-12’s simple rear peep sight (top right). USAS-12’s front peep sight (bottom right).

“The present shotgun firearm can be accurately used at a distance of at least 100 yards. At this distance the operator of the shotgun will be able to disable his target. This is from but a single shell. However, when used in the automatic mode, this firearm will fire shells at a rate that a fairly large area can be covered. For instance, this firearm is capable of firing at least 360 rounds per minute. In the semi-automatic mode the number of rounds per minute will be controlled by the person using the firearm.

Thompson, a fan of the FN FAL, prefers the cocking handle on the left side.

Another significant feature of the present firearm is its simplicity. The firearm consists of very few parts, but yet is highly reliable and is not subject to shell misfirings. That is, there is a positive injection of each shell into the firing chamber and a reliable ejection of the spent shells from the firing chamber. In the past it has been difficult to feed shotgun shells from the magazine into the firing chamber under high rates of firing due to the recoil of the firearm and other problems. The positive injection of shells is primarily the result of the angle of the magazine with relation to the firing chamber and the particular bolt carrier and bolt arrangement that is used in this firearm. (Patent # 4,930,399)”

Thompson in the midst of a three-round burst with the USAS- 12; note the muzzle has climbed slightly.

Among the statements bordering on hyperbole are that the shotgun is accurate to 100 yards and will disable its target at that range with a single shell. It is also capable of firing at least 360 RPM. The patent document also states: “a fairly large area can be covered.” As one of the intents in developing a select-fire shotgun was to put lots of buckshot down range quickly to break an assault, “area coverage” does have some validity. One of my first reactions upon learning of the rate of fire of the USAS-12 was how it would reliably feed tubular shaped shot shells at that rate. The patent document does explain the process well:

Thompson firing a two-round burst from the USAS-12; note the butt has climbed slightly on his shoulder.

“These problems have been resolved in part by providing an angle of about 4 to 6 degrees, and preferably about 5 degrees for the magazine with relation to the breech of the firing chamber. This angle of the magazine compensates for the slight recoil of the weapon when it is being fired. In addition, there is the use of a unique arrangement between the bolt carrier and the bolt of the firearm. The bolt carrier is in essence a piston, which is actuated by the gases from a fired shell. On the front of the bolt carrier is the piston head which is pressurized upon the firing of each round. At the rear of the piston there is a downwardly extending section, which is attached to the bolt. This downwardly extending section has two apertures and a forwardly extending cam. One of these apertures is elongated in shape and receives a travel-limiting pin while the other aperture is elongated and at a forward end has a downwardly extending portion. In this second aperture a roller is inserted. The forwardly extending cam fits into a locking pin on the bolt which serves to lock the bolt and bolt carrier.


Result of three rounds of #4 Buckshot fired at 25 yards on full auto. The sights were off slightly to the left.

A key feature here is the roller that is in the second aperture. This roller rides on the roller track in the receiver. The bolt contains at the forward point of travel of the roller a slight indentation into which the roller will fall in conjunction with falling into the downwardly extending portion in the second aperture. It is this roller and the operation of this roller in the bolt, bolt carrier and roller track which provides for the correct timing between the bolt and bolt carrier. This roller assembly also absorbs the torque moment on the bolt upon the weapon being fired. Another feature of this weapon is with regard to the face of the bolt. On the periphery of the bolt face, which contacts the shell there is on one side an extractor pin and on the other side a sub-extractor pin. However, there is also at a point above these pins a stabilizing pin for stabilizing the shell against the bolt face.”

As interesting as the USAS-12 is, Thompson would choose a more traditional home defense shotgun such as this Mossberg 590A1. Don’t laugh at the bayonet. It offers good intimidation effect and also lessons the chance of someone trying to grab the shotgun.

I had a chance to fire a USAS-12 that had been evaluated by a couple of law enforcement agencies but not adopted. My first reaction when I picked up the USAS-12 was that it was heavy, almost twice as much as a Remington 870 Tactical that I normally use. Though not a “tactical, carry method,” I found the carry handle useful for toting the USAS-12. The sights were familiar, as I own a couple of Daewoo rifles, the sights of which they resemble. Though heavy with the 20-round drum in place, the pistol grip and good-sized forearm helped keep the shotgun balanced in the hands. The selector switch, with positions for “SAFE,” “SEMI,” and “AUTO,” could be reached by the thumb of the shooting hand while on the pistol grip. By switching the cocking handle and ejection port cover, the USAS-12 may be set up for right- or left-hand usage. I prefer the cocking handle on the left side, having done a lot of shooting with FN FALs, so the ejection port was operable on the right side. The magazine release button is on the right side and is a little small but workable.

Thompson also still likes the reliability of a traditional Remington 870 tactical shotgun. The shell carrying capacity of the side-saddle and the stock offers a lot of firepower.

I found it took a little practice to push the drum home quickly and securely, while the box magazine was faster. The butt plate is ribbed, which I found useful as even though I pulled the USAS-12 into my shoulder tightly, the butt did ride up a bit on full auto fire. In test firing the USAS-12, I wasn’t as optimistic as the writer of the patent application and fired at silhouette targets at 25 yards. I fired two drums loaded with #4 27-pellet buckshot shells and two box magazines loaded with 00 12-pellet Buckshot shells. (Later, we tried slugs and miscellaneous shot loads and all fed.)

I found two-round bursts easy to keep on target; three-round bursts harder but doable; four-round bursts difficult. However, it was possible to fire two or three rounds, layoff the trigger for an instant, pull the butt back against the shoulder hard, and fire another burst. At 25 yards, with two or three-round bursts, the pellets were staying on the target. I noticed, though, that even on some three-round bursts the impact point climbed to the right and high indicative of the torque of the shotgun on full auto. On the other hand, the sights seemed to be off to the left. I am definitely glad I got the chance to shoot the USAS-12. Having said that, I understand why the local law enforcement agencies that had tested the USAS-12 did not adopt it. Possibly in the military application of being in a static position and needing to break a mass attack, the USAS-12 would have been effective. However, from my perspective, the Remington 870, Mossberg 590, Remington 11-87P, or Benelli M3 will fulfill my combat shotgun requirements.

If you have any thoughts or comments on this article, we’d love to hear them. Email us at

GET THE NEWSLETTER Join the List and Never Miss a Thing.

Recommended Articles

Recent Videos

FN America has brought out a scaled up version of the 9mm FN 509 pistol chambered in 10mm Auto. Firearms News Editor-in-...

Federal's “Punch” line of Personal Protection Ammunition

FN America has brought out a scaled up version of the 9mm FN 509 pistol chambered in 10mm Auto. Firearms News Editor-in-...

KelTec's new KSG410 and R50!

FN America has brought out a scaled up version of the 9mm FN 509 pistol chambered in 10mm Auto. Firearms News Editor-in-...

Liberty Ammunition

FN America has brought out a scaled up version of the 9mm FN 509 pistol chambered in 10mm Auto. Firearms News Editor-in-...

Springfield Armory 9mm Saint AR15

FN America has brought out a scaled up version of the 9mm FN 509 pistol chambered in 10mm Auto. Firearms News Editor-in-...

Rock River Arms New ARs

FN America has brought out a scaled up version of the 9mm FN 509 pistol chambered in 10mm Auto. Firearms News Editor-in-...

MKS 10mm Hi-Point Pistol

FN America has brought out a scaled up version of the 9mm FN 509 pistol chambered in 10mm Auto. Firearms News Editor-in-...

Magpul FDP-9

FN America has brought out a scaled up version of the 9mm FN 509 pistol chambered in 10mm Auto. Firearms News Editor-in-...

Legacy Sports New Howa Rifles

FN America has brought out a scaled up version of the 9mm FN 509 pistol chambered in 10mm Auto. Firearms News Editor-in-...

Aero Precision Bolt-Action Rifle Line

FN America has brought out a scaled up version of the 9mm FN 509 pistol chambered in 10mm Auto. Firearms News Editor-in-...

American Tactical, Inc. New Single-Shot Folding Rifle

FN America has brought out a scaled up version of the 9mm FN 509 pistol chambered in 10mm Auto. Firearms News Editor-in-...

American Tactical, Inc. 9mm GSG-9 Pistol

FN America has brought out a scaled up version of the 9mm FN 509 pistol chambered in 10mm Auto. Firearms News Editor-in-...

FN America 510 Tactical 10mm

Firearms News Magazine Covers Print and Tablet Versions

GET THE MAGAZINE Subscribe & Save

Digital Now Included!


Give a Gift   |   Subscriber Services


Buy Digital Single Issues

Magazine App Logo

Don't miss an issue.
Buy single digital issue for your phone or tablet.

Buy Single Digital Issue on the Firearms News App

Other Magazines

See All Other Magazines

Special Interest Magazines

See All Special Interest Magazines

GET THE NEWSLETTER Join the List and Never Miss a Thing.

Get the top Firearms News stories delivered right to your inbox.

Phone Icon

Get Digital Access.

All Firearms News subscribers now have digital access to their magazine content. This means you have the option to read your magazine on most popular phones and tablets.

To get started, click the link below to visit and learn how to access your digital magazine.

Get Digital Access

Not a Subscriber?
Subscribe Now

Enjoying What You're Reading?

Get a Full Year
of Guns & Ammo
& Digital Access.

Offer only for new subscribers.

Subscribe Now