Fritz Mann Model 1921: Chamber-Ring-Delayed Blowback

In 1920, Fritz Mann of Germany patented the idea of cutting a shallow ring in the chamber of a pistol as a delaying mechanism. When fired, a cartridge case would expand into this groove, thus requiring more time and energy to push the case out of the chamber and effectively delaying opening. This allowed Mann to reduce the weight of the operating parts of his model 1920 semiauto pistol in .25ACP (aka 6.35mm Browning). The gun was designed to be as small and as light as possible; a true pocket pistol. Thousands of them were made in 1920 and 1921, although he gun failed to see long-term popularity. For more information, I recommend Stefan Klein’s article on Ed Buffaloe’s web site:


    • Wonder if Nitinol could be used (I know I say that about most things) but, simply… I.e. A ring on the case, to go into a hole for said “ring” in the chamber… Bang! = Heat = Niti swells = Chamber fills = slower opening. Maybe try it with .762x33mm carbine tied to a fence, pull a string; to depress the trigger. Pop over have a nosey.

        • Albeit it needs “the niti” to cool a bit to de-swell… But maybe there is a medium I.e. As pressure blowing it out/extractor pulling on the case… So it might just provide a WEE! Stretch (as per normal chamber ring delay; but with increased filling of chamber) but then via said forces give way… The WEE! bit, I emphasise; because it is all over quick- bullet exits barrel so maybe it is wee enough, obviously with that depends how quick the niti actions… Maybe combine both; brass chamber ring as per, backed up by niti (give the nitinol a chance to expand) might work… Be good if it did.

          • It would really; Point being negate the need for mechanical delay/locking, the round does it itself.

            If it works in a .30 m1 fiddle some more; might work in .223 etc, even with more chamber rings/niti rings/brass/normal chamber rings. Ways… Probably anyway, 1921 100 years ago; pretty cool!

          • Thickness/angle/setting of niti ring, would be to assist de-swelling without temp cooling, much… Anyway all good.

          • Theoretically I am saying that could work; on the premise that WEE! extra expansion vs Brass, is enough. If the timing can be made right; which maybe it can’t be, I don’t know.

            Anyway I won’t go on, and on he he.

          • I will honest, stop now; but I put it to you niti apparently must atomically change. 100,000psi it just must; thus I am saying, that is the delay.

          • Be great though as a mk108 type cannon, with niti detonation and this type of round we could increase it’s destructive power ten fold; high pressure, which is what… We may need for, robots.

            They have the advantage; they don’t bleed etc.

            Can be addressed.

          • 100 fold ideally; seperate subject under the terms of shutting up prior, I am unilaterally allowed to rant about anti robot measures which may or may not be needed he he.

          • Pah, thats rubbish “for once” we need big fuck off terminator rounds. Mk108. At speed, with more power; but with a cheap gun.

            Yay!! He he.

          • “(…)mk108 type cannon(…)increase it’s destructive power ten fold;(…)”
            Unless it is intentional show of disdain it should be MK 108. I do not get how you would to get desired result, remember that it used Minengeschoß which already have high ratio of HE filler mass to overall mass of shell. How your solution can make that ratio higher?

          • Niti detonators: round is detonated as per now but, its quicker no mech, niti change detonates primer, then round is armed and spat out under a higher pressure than the stubby barrel via thinking of the above as being in the projectile & shell more gas.

          • Minengeschoß; longer barrel with mk108 action I mean.

            Cheap. If we ever fight migs, with eurofighters.

            The best design will actually be the mig17 as they will be all dead at the cost of trillions in days.

      • “(…)ring on the case(…)”
        Are you sure that such case, i.e. composed of vastly different materials could be stored as effortless as classic one? Also what about price, note that cases are often ejected and thus used once.

  1. A perfect example when a competent mechanic thinks that there are no secrets in machine gun building. 😉
    Technically, an almost perfect design, while completely inadequate for its purpose.
    Due to the tiny grip of this pistol, it was almost impossible to hit anything on purpose.
    And due to the overall small size and wacky ergonomics, it was very easy to accidentally hit yourself.
    In addition, he also had the habit of biting.

    And the field strip is limited to the removal of the barrel. This is enough for service.

  2. Walther 9 of the same era designed in the due course was slightly heavier but shorter than this .25” pistol… This means there would be no hopefull market chance… But the delaying concept seemed hopefull… For somewhat heavier caliber…

    The machining cost seems nearly equal with standart blowback models if the one piece frame was not made of investment casting method which was unpopular at that time…


  3. Somewhere I read about a FLUTED chamber for delaying blowback. The flutes are blind, i.e., they stop short of the cartridge mouth and thus don’t admit gas to the chamber. As with the ring method, the delay is caused by the case expanding into the flutes during peak pressure, and then springing back as pressure drops. (Good old brass will do that.) Thus the stresses on the case are longitudinal rather than radial, and might (he theorized hopefully) be less likely to cause separations.

    The flutes are extremely shallow, and I have to wonder wonder how long they last.

  4. A fascinating little pistol – with the emphasis on little. Is there any indication as to how popular such small caliber pistols were (there certainly seems to be a number of these designs)? Given that these seem to be quite ineffective and even had ‘modest presence’ e.g. hardly a strong deterrence if flourished or fired for effect.

  5. “(…)how popular such small caliber pistols were(…)”
    6,35 mm Browning was popular cartridge in Germany during interbellum. For example according to there were made 330000 examples of 6,35 mm Mauser 1914 automatic pistol and this one of numerous models, see
    Even the bigger ORTGIES automatic pistol was available in 6,35 mm

  6. After looking at Ed Buffaloe’s article I am glad to have this video and see how the innards were actually put together. I think this is a fascinating design — a solid frame in one piece with all the working bits inserted from front, back, and bottom. Even aesthetically the shape is intriguing: the sloping surfaces rising to an almost-apex at the top strap, the huge curve for the web of your hand, a trigger guard that can double as a knuckle-duster. Many thanks to Mr. M for bringing this to us.

  7. “Everywhere I hear the sound of marchin’, chargin’ feet, boy
    ‘Cause summer’s here, and the time is right
    For fighting in the street, boy”

    Given what was going down in the streets in Germany in the early Twenties (The Allies thought it was appropriate to allow the polezei to carry machine pistols) with gangs to yeggs from both the Left and Right battling it out daily, we can quote an old Tammany Hall operator, ““I seen my opportunities and I took ‘em” (George Washington Plunkitt)Hey, the market was there to be filled, The gun looks well made and finished, as you would expect from a German gin make of the period. I like it ! I may well have bought one back in the day, Dad, can I borrow the time machine, tonight….

    PS: OK, I promise to avoid funny little ex-corporals with tooth brush mustaches

  8. Substitute “gun” maker” fi=or “gin maker”, although the idea of German made Gin sounds interesting. Ian, can we get to try some on your next Q&A

  9. Here’s a totally disassembled Mann:

    The bolt is hanging up on the sear, which is pinned into the frame inside the very back of the web strap. (Perhaps pulling the trigger releases the bolt, like a Carcano rifle?) I believe the scallop cut on the bolt acts also as disconnector.

    Here’s a blog thread about it:

    Wherein you find other cleverness, such as the magazine return spring and the trigger return spring were one, really odd, stirrup-shaped spring.

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