Less than 300 of the Kimball .30 Caliber Carbine Auto Pistol were produced back in the 1950s. The operating system is fascinating. It is straight blowback, but upon firing the case expended into a ring machined into the chamber. The slide was force to swaged the case back to shape in order to extract it. In theory the swaging took long enough for pressure inside the chamber to drop to safe levels. Extracting a squib round must have been a quite a process!
Mr. Bruce Dot Com quotes the Canadian-Firearms Digest V1 #851 ...
So he had an excellent way to lock the breech CLOSED until the pressure dropped, right? WRONG. He gouged an annular ring around the inside of the chamber. On firing, the case expanded into the ring, and blowback forces swaged it back down to size as the cartridge pushed the slide back.
The NRA was highly interested in this new "wonder30." They got one of the first specimens off the line, and fired it. In a VERY short period of time, it stopped working, with the slide unwilling to move. They disassembled it.
The design allowed the slide to run back until it hit a vertical post at the rear of the grip -- again, like the .22 rimfire Colt or High Standard. The post was so battered and distorted by trying to stop that light slide that it had mushed out to the sides and jammed the slide.
It sees swaging was not enough to slow down the slide. Gas operated pistols with a locking bolt, and revolvers, are much better suited to high powered rounds.
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