This Day in History: the UD42 is Patented

The UD42's magazines were attached to each other for faster reloads. (Rock Island Auction Co)
The UD42’s magazines were attached to each other for faster reloads. (Rock Island Auction Co)

U.S.A. –-( On October 14, 1940, Carl Swebilius of High Standard patented a submachine gun chambered for the 9x19mm cartridge.

While it was visually similar to the Thompson submachine gun, the guns were decidedly different. Swebilius’s gun fired from an open bolt at a rate of approximately 880 rounds per minute. Fitted with an 11-inch barrel, the gun weighed approximately ten pounds. Its magazines held 25 rounds and were affixed to one another face-to-face, allowing for rapid reloads.

Initially, Carl sought to offer the gun to foreign countries, and he retained a man named Frank Jonas to handle the overseas contracts.

Right away, though, things did not go smoothly with this new design. For starters, High Standard was focusing its energy on fulfilling a British contract for 12,000 .50 caliber machine guns to be delivered in just 10 months. This meant that they had little time or resources to devote to this new submachine gun, no matter how lucrative the other overseas contracts might be. If the gun was to be produced, another firm would have to do it.

Essentially just a company on paper, the newly-created United Defense Supply Corporation in England obtained the rights to make the gun. Through connections with the British Purchasing Commission, United Defense managed to obtain a somewhat spurious endorsement by the British military for the gun, which was now being called the UD42. The Dutch soon placed two orders for 7,500 units each.

Unfortunately, United Defense had no engineers to work on the gun and no manufacturing facilities to produce the finished product. Contracts in hand, United Defense had to secure a subcontractor to actually make the submachine guns for them.

Eventually, Marlin Firearms agreed to produce the guns, but more troubles arose in short order. High Standard failed to provide adequate drawings, and when they finally did so, they were not adequate. In March 1942, Marlin noted that “no company could have made a completed gun on the prints supplied by High Standard.”

United Defense appeared on the markings, despite being essentially just a paper company. (Rock Island Auction Co)

Another issue voiced by Marlin was that they “were supposed to provide a gun that shoots and that is all,” but that a Dutch inspector was insisting on inspection of individual parts (not completed guns) and that the parts had to be interchangeable. Marlin maintained that “this was not in the contract,” and so it wasn’t their fault that the guns did not interchange. The Dutch government was understandably perturbed, and Marlin went to great expense re-tooling aspects of their factory in order to finally achieve parts interchangeability.

By the time all of the kinks had been worked out, the need for the UD42 in the Netherlands had passed; Germany had already invaded and occupied the country, so the plan for using the guns as a means of resistance was now moot. Of the 15,000 they had contracted for, only 800 were actually delivered. The other 14,200 remained stateside.

Around the same time, the United States began to take an interest in the UD42. Their biggest hang-up with the design, though, was the caliber. If the US was going to supplement or replace the Thompson with the UD42, they were not going to muddy the waters by introducing another caliber into the mix. As such, if United Defense wanted to secure a contract with the US government, they’d have to alter the design so that it would use the .45ACP instead of the 9mm cartridge.

A small number of prototype UD42s in .45ACP were produced and tested by the US military, but time was of the essence, and it took High Standard six months to produce just five prototypes. Reviews were favorable, but there were more hurdles in the way. Disagreements regarding contract terms and royalties were exceptionally complicated between Marlin, High Standard, United Defense, and the US government. All of this took valuable time to negotiate, and once an agreement had been reached, it was too late.

Because of this issue of money, it should come as no surprise that the US sidestepped the UD42 and decided to adopt the M3 “Grease Gun” instead. It was cheaper, faster, and easier to manufacture, being made from stamped parts instead of machined parts, as was the case with the UD42. The M3 also boasted a higher magazine capacity of 30 rounds while the UD42’s magazines only held 20 rounds of .45ACP.

The M3 was adopted in place of the UD42. (Rock Island Auction Co)

Despite missing out on two government contracts and failing to become the replacement for the Thompson submachine gun, the UD42 would still go on to see action in World War II with the help of the Office of Strategic Services (OSS).

Today, there are only a handful of them that are known to be legally registered in the US, which allows them to be legally bought and sold. As such, if you can find one for sale, it won’t come cheap. I have found auction records of just four over the past ten years, and the prices ranged from $13,800 to $23,000, with the lowest one believed to have been a reactivated war trophy, or REWAT. The least expensive gun in original condition sold for $17,250.

About Logan MeteshLogan Metesh

Logan Metesh is a historian with a focus on firearms history and development. He runs High Caliber History LLC and has more than a decade of experience working for the Smithsonian Institution, the National Park Service, and the NRA Museums. His ability to present history and research in an engaging manner has made him a sought after consultant, writer, and museum professional. The ease with which he can recall obscure historical facts and figures makes him very good at Jeopardy!, but exceptionally bad at geometry.

0 0 votes
Article Rating
Inline Feedbacks
View all comments

Logan, thanks for another interesting history lesson.


You learn something every day, no matter how old you are (unless you’re a Democrat or liberal). Very interesting and informative. Thanks.


Pretty interesting article.