The P7 was one of the most interesting and original handgun designs of the last few decades. Originally created for West German police trials, it was chambered in 9x19mm. As it became popular beyond Germany, the question arose of it being offered in additional calibers. The P7M10 was released in .40 S&W (that’s a story for a different video), but it was never put into serial production in .45 ACP, despite H&K USA pushing heavily for it.
On the technical side, the .45 ACP cartridge caused problems with the design’s gas-delay system. It simply did not work reliably with the bullet weight and gas pressure of the .45 cartridge. Instead, H&K engineers replaced the gas piston with a hydraulic buffer or damper. However, only a total of 6 prototype were made in the mid 1980s, as the German branch of the company was against its production (presumably because they did not think it would sell well enough to justify the production retooling costs it would require). I believe this example (serial number 2) is the only one in the United States today.