When the Bren Ten pistol came along in the early 1980s, it caused a great deal of interest and speculation. The gun was loosely based on some of the features of the Czech CZ75, a 9 mm service auto that could not even be legally imported into the United States from Czechoslovakia. It was one of the early "Wondernines" and even had a cocked-and-locked carry feature.
Jeff Cooper had conditionally endorsed the CZ at the same time that he condemned its less powerful cartridge. When a pair of Southern California entrepreneurs—Dornaus and Dixon—came up with a CZ based pistol, to try and supplant the 1911 .45, it needed a new cartridge to stand a chance.
Accordingly, they were part of a developmental effort that produced the 10 mm Auto. The Bren Ten story is as much the story of a cartridge as it is the story of a pistol. What happened in just a few short years is fascinating. The 10mm Auto was probably just a little more powerful than it should have been and the Bren Ten pistol had no end of production problems.
Ultimately, the project failed. It was a grand and glorious effort to give combat handgunners a better arm. The story is best told in a great book, "Bren Ten, The Heir Apparent" by Ronald Carrillo. No gun book that I know of was ever as thoroughly researched and accurately reported. Carrillo did a great job.