Karl Brügger, CEO of B&T, is a true gun nerd and avid competitive shooter. When he got his hands on the Spectre SMG with its quad-stack magazine and weird DA/decocker fire control system, he thought it was really neat. So neat that he decided to buy the project from its Italian creators and put it back into production. But they had thrown out all the drawings and tooling when the gun wasn't successful, and so Brügger had to recreate it from scratch on his own. Cue the Karl's Hobby 9!

Without Spectre magazines to use, or the tooling to make them, B&T instead found a batch of quad-stack Suomi magazines and used those. They faithfully recreated the DA firing system and decocker, and decided to make a limited batch of 222, because this was just a fun side project and not something that would be commercially popular. Except that the sold out really fast. And so another batch was done, this time using APC-9 magazines, since the supply of Suomi mags had been exhausted. Then when they found some Suomi drums, they did another limited batch for those. All of these sold out rapidly, and so the project grew legs. Next up, it became the KH-9 Covert, because what makes a gun cooler than adding folding bits to it?

It remains a limited-production item made in both Switzerland and in the US. Turns out that Karl Brügger isn't the only guy who thinks they are really neat...