How Does it Work: Blow Forward

The blow forward system has only bee used on three commercially-produced firearms: the Schwarzlose 1908, Hino-Komuro, and Mannlicher 1894 (The SIG AK-53 uses a forward barrel movement, but in conjunction with a locked breech). It offers a simple system with a theoretical extra margin of safety because the side cannot come backward off the gun, but at the cost of substantially increased felt recoil. Once the blowback system was out of patent protection, there was no convincing reason to use the blow forward mechanism.



  1. I though that blow forward might be option for someone wanting (very) high Rate-of-Fire sub-machine gun. I start searching if anyone made blow-forward sub-machine gun and I encountered this (see 1st photo from top): described as Stoehr machine pistol in .22 Magnum and said to be blow-forward. But it really is? What is purpose of using muzzle brake(?) on blow-forward fire-arm?
    However, blow-back principle also allow great Rate-of-Fire, note Villar-Perosa
    which despite being delayed blowback offered 1200…1500 rpm from single barrel.

    • As for the muzzle brake on stoehr, it looks more like its threaded, to me, or maybe some creative turning.

      • Can you please help me to find information on the patent of the direct blowback system? Was it patented before locked breech automatics existed?

    • I believe that’s not a muzzle brake, but a grooved section for grasping. This gun appears to be a blow-forward, open-bolt gun; it’s cocked by pulling the barrel forward, and the sear (integral with the trigger) catches on the wider flange behind the grooved section. Pulling the trigger drops the sear and releases the barrel to slam backward and fire.
      This picture shows a better view of the grooved section:

      The cartridge feed is especially peculiar — it’s particularly suited to a blow-forward system, as otherwise the cartridge feed would have to reciprocate with the bolt.
      Apparently the feed “belt” is a metal band, with ratchet teeth cut in the top edge. The feed pawl is exposed on the right side of the gun, and is apparently driven by a cam track milled in the top of the barrel.

  2. One of the original designs by the Mexican sub-machine gun Rafael Mendoza enterprise was a blow-forward design.

    Also, as far as prototypes vs. the Hino-Kimura pistol and the Mannlicher 1894 and the odd Schwarzlose 1908…

    W. Darrin Weaver, _Desperate Measures: The Last-Ditch Weapons of the Nazi Volkssturm_ (Ontario: Collector Grade Pubs., pp. 250-253: The “Coenders/ Röchling Volkssturmkarabiner.” Only one in existence–possibly ever made. 5-shot fixed magazine, 7.92x33mm blow forward “semi-automatic, magazine fed, blowback [sic, blowforward!], air-cooled weapon. The nusual features of this carbine are the use of a forward recoiling barrel and a double-action trigger mechanism similar to that used on double-action revolvers.”

    We now know thanks to Ian’s recent demonstration of a defective AK-53 from SIG-Neuhausen auto-rifle, that while the barrel reciprocates forward, extracting the empty 7.5x55mm case that remains on the breech face as the chamber moves away from it, and then ejecting it, then, on the return stroke having the barrel feed ramp move over the top cartridge in the magazine, locking the barrel into the receiver with flaps, and recocking the arm, that it is not a blow-forward design, but rather an odd gas-system. Seems as though the gas piston compresses two springs, one of which is over the barrel return spring, locks the two together, and then unlocks first the barrel spring to force the barrel forward, and then the second to return everything into battery…Yes?

  3. I might also point out, after ruminating on the oddities of the SIG-Neuhausen AK-53, bizarre variation-on-the-theme, that the stock furniture is essentially the same as the notoriously over-complex/over-engineered Furrer toggle-lock 9mm SMGs that were relegated to indoors/fortress use while the more conventional–and certainly cheaper!–Suomi/Hispano-Suiza 9mm MP/SMG was used “out of doors” by the Swiss militia-based armed forces.

  4. I think for b.f. to work, you need to have rifled barrel, as the bullet traveling down the bore engages rifling and pushes the barrel front. Without it, I doubt it would move sufficently to rechamber new round.

  5. The late Robert Hillberg, a very successful American designer for High Standard and others, also designed a blow-forward SMG, but it was never produced.


  6. Blow Forward works in the same manner which blowback samples follow: the forward push of the gas pressure to the bullet back forming as a plug from breech to the muzzle through the bore. Same momentum applicable for blowback is also valid for the blow forward. The gas escape, mass comparision, friction might effect the happening at positive or negative sides.

    • I’d say blow forward is not so simple as “blowback in reverse”, and that maybe we do not understand, for now, fully all the forces at play.

      • During the discharge, bullet is a plug in the barrel from case mouth to the muzzle as if making the bore like a blind tube. Gas pressure pushes the breech blog at rear and pushes that blind tube forward and if the blind tube is forwardly movable, it blows forward.

  7. I hate to be techno-grammatically picky, but in case anyone comes across this video and commentary in the far future, I must point out that several times Mr. M said that the “slide” blows forward — we know he meant barrel & chamber acting as a slide in reverse. And he said the recoil kick is hard because the “slide” doesn’t recoil — we know he meant breechblock.

    He has also been guilty of mixing up mainspring and recoil spring as terms, and yards, meters and arshins, but of course to have this channel at all is worth the occasional flub.

    Was not the Hino-Kimura not just blow-forward but also slam fire? Have to review his video on it.

    • Yes. According to Handguns of the World by Ezell, the barrel began each cycle in the forward-most position. Pulling the trigger released it to come back under spring pressure, scoop a cartridge from the magazine, and slam it into the fixed firing pin in the standing breech.

      It would have been very simple to make the Hino-Komura a true selective-fire machine pistol for this reason. I believe the Mendoza RM-1 submachine gun prototype worked on a similar principle. It drastically simplifies the weapon’s mechanism, most obviously by eliminating the need for a movable firing pin, striker and/or hammer mechanism.

      Of course, it also rather mandates that the weapon be kept in Condition Three (uncocked, empty chamber) at all times for safety reasons, as Condition One leaves the chamber and magazine open, just as on a typical slamfire SMG like the Sten or MP38/40.



      • Rate of fire would be interesting, how much that barrel moves forward during firing, I suppose it would be mac10 high.

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