Kimball .30 Caliber Carbine Auto Pistol

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.

Steve Johnson

Founder and Dictator-In-Chief of TFB. A passionate gun owner, a shooting enthusiast and totally tacti-uncool. Favorite first date location: any gun range. Steve can be contacted here.


  • bbmg

    “Gas operated pistols with a locking bolt, and revolvers, are much better suited to high powered rounds.”

    … or you could simply hack the ends off an M1 carbine 😀

    • DW

      My friend, M1 Carbine IS gas operated…

    • Sian

      What was that packed in, topiary foam? *boggles*

  • Trev

    Please proofread. For the love of all that is Holy.

  • Peter BE

    The last version of the makarov, with higher mag capacity and higher pressure 9mm Mak round, uses a helical groove in the chamber to allow for the pressure to drop before the slide opens.

  • higgs

    I fired a 30 carbine 1911 style pistol a while back. Hell of a handgun

    • DW

      AMT Automag?

      • higgs

        Yeah, AMT Automag III. thanks for the life of me i couldnt remember that.

  • sizzla

    this sounds like a recipie for case head seperation but the most common malfunction was as slide flying of at great velocity

  • Foetus

    I find it beautiful.

  • Flounder

    LOL the story about the failure is actually super funny since the seecamp pistol in all of it’s calibers uses this exact same method of “chamber delayed blowback”. Although they are only in 25acp ? and 32 and 380. 30 carbine is a pretty beastly round for just a blowback pistol.

    The seecamp may use multiple annular rings in the chamber not just one… And hi-standard made a 380 version of this that did go into production… the G-380 I believe. YES! The G-380 just gunbroker-ed it and a few popped up.

    STEVE!!! Please do a follow up on these types of guns! i’m sure with all of the people you know you could dig up quite a lot on the topic. Maybe some pictures of once fired brass next to factory brass? Or pictures of the chambers?

    Oh and I believe people sometimes mill a ring into the chamber when shooting pistols suppressed to delay the slide opening too early due to the increased pressure of shooting with a can.

  • armed_partisan

    Someday soon, I’m gonna build a .30 Carbine pistol based on J.D. Pedersen’s Remington Model 51 design. They built it in .45, I might build it in 9mm, but I want one in .30 Carbine, so that’s what I’m gonna build (as soon as I get my lathe running…).

  • cm smith

    Other pistols with annular rings in the chamber: … the Detonics mini DA 9 mm of 25 years ago …. the High Standard 9 mm protoype for the 1950’s US trials … Colt Gold Cup .38 spl. … …

  • In their advertisements, Kimball also announced their intent to make .22 Hornet, .38 Special, and .357 Magnum versions.

  • Lawrence Tommer II

    I LIVE NEXT DOOR TO ME KIMBALL HE GAVE ME A PISTOL THE OTHER DAY AND I’M SO IMPRESED WOW. He 88 now and told me why he stoped working on his pistol . He ran out of backers the man helping him tried to steel his gun so he hid it. Until now.