BSW Prototype Gas-Operated Pistol (Video)

In 1936 or 1937, the BSW company (Berlin-Suhler Waffenwerk) produced a small number of prototype pistols for German Army trials. These trials were eventually won by the Walther P38, and for good reason in this case. The pistol BSW submitted was a gas-accellerated blowback design, with an aluminum frame, stamped slide, 13-round magazine (in 9×19), and double-action-only shrouded-hammer firing mechanism.

I had the opportunity to try shooting one of the 3 surviving examples of this pistol thanks to the generosity of a reader named Steve (thanks, Steve!). This is one of those cases where it seems that the trials board evaluating guns made the right conclusion – this pistol was finicky to disassemble, quite large, and had harsher than normal recoil because of its light weight, high bore axis, and blowback mechanism. Its 13-round magazine was a nice touch, but one of very few positive elements in the gun.


  1. What designer want achieve with slide serration near muzzle rather than opposite end?
    I am aware that Browning’s Colt M1902 automatic pistol also has serration like this, but in later models this was dropped in favor of serration on opposite end.

  2. I don´t know what´s the point of having an accelerator lever in this pistol. It seems that they were tinkering around with the action of this prototype. A true gas actuated locking lever is a more plausible concept, but perhaps it didn´t performed well enough actually. Who knows? A slide serration near the muzzle would make sense to tip down the lever with index and thumb and then rack the unlocked slide, IMHO.

    • I think that’s what you originally did, they angled the cut in the lever to engage the slide piece thus / towards the muzzle so the slide would catch it and pull it up towards the barrel- Locking it, then the gas would unlock it… However to chamber a cartridge initially you would need to actuate the lever manually, then they figured that was a hassle and essentially just had the slide snag on it to slow it down during blowback negating the need for the gas port, but they perhaps thought it would aid in terms of reliability however superfluous this maybe.

  3. What a confusing approach. Design seems very simple as the gas actuating lever delocking the slide and barrel engagement. But, what enables to retract the slide freely. There should be a motion factor just working when the gun in firing position. It may be a small gas piston under the chamber forcing the gas lever remaining in locked position and when the bullet leaves out, it should be needed a so called “Accelerator” to quicken the unlocking action.

    • hi Strongarm

      I am going thru your notes again and it seem to me that they are unrelated to each other (unless I do not reed ten right) as you react to other contributors. Also it looks that this may have been your first observation.

      My interpretation why this works while, as you correctly state because the port is at muzzle, is the fact that even after bullet is out, there is still residual pressure which lasts couple of milliseconds. This is apparently enough to get things going. Most likely, theories aside, this was developed by trial and error.

      • Hi, Denny,

        You are right. A working specimen of very different concept made me thought on various paths to find an optimum approach about how it would be possible with existing elements and l wrote somethings unreleated.

        According to my limited knowledge, this pistol is made with an intention of gas impingement unlocking and manually actuating the unlocking lever to retract the slide for initial loading the chamber. Horizontal serrations at lever’s front and slide serrations near the muzzle enabling simultaneous actuation of lever and slide also confirm this. There should be neither a static friction concept nor an inertial hesitation presented in the concept. As you know, Static Friction works best with different metal types and hardened steel, a must for heavy working contact surfaces, should be one of the worst. What German Designers had not counted per se, is the leverage lenght and mass of gas release arm which would swing downwardly at instant of discharge through inertia. By means, the very small contact surface of locking bar in front of muzzle section of slide, would slip off from the lever’s opposite and releases the slide before the time which designers computed. The pistoi Ian fired may have a broken teeth on the lever and the pistol can be manipulated easily by this cause. Accerelation might be thought for quicken the slide for getting use of residual gas pressure by cause of unlocking gas obtained very near the muzzle with a short barrel. But with this existing configuration of gun, it functions to open the barrel’s back earlier than expected. The mass of slide seems to manage to work in blowback system and high felt recoil should come from the fact of this working manner with no bumper element. In short. This sample gun is a defected one working in accerelated blowback operation and German Staffs chosen the P38 were quite right.


  4. German designers loved kinetic locking mechanisms, so that the gun would lock when the slide moves back fast, until the gas mechanism removes the locking catch. If moved slow the slide could move the lever out of the way for easy racking.
    Of course that required a precise interaction of angled pieces for the desired effect, and the prototype might just have lost that precise alignment(or someone in the last 80 years took a file and straightened out that edge to smooth the operation).

    • Brilliant finding. At instant of firing, the lever tends to keep its state against to the recoiling and muzzle rising gun as pressing the locking bar tightly against to its over angled upper cut, therefore, halting the slide backward travel, and when the slide manually retracted, the lock bar rides over the rear sloped mini lug without getting contact with upper sharp angled surface.

      • I think it just snags like you said the R51 does, and sort of agreed with, the gas thing is niether here nor there, I reckon it’s a remanent of the original design, that actually locked but you needed to manually operate the lever initially, a bit like that pistol we said could have a strong spring because it broke open, a manual thing…

    • Mu, I think you are right. A blowback-operated pistol in 9mm has no need for an accelerator, especially when it uses a lightweight aluminumm frame. I also believe that they wanted the lever withstand the sudden force during firing, and allow the shooter to retract the bolt without actuating the lever.

    • I believe that you are substantially correct. My quibble is with the fast/slow slide speed argument. I would substitute a high/low pressure argument. Because the rear of the slide bar makes contact with the gas lever lug above the gas lever pivot point, it can push the gas lever down only if there is low friction. Under high pressure from firing the friction is too great and the slide bar wants to force the gas lever up.

      Ian clearly demonstrates the accelerator function. IMHO the magazine probably needs a stiff spring to overcome the transition between double stack and single stack. With a full magazine stripping of rounds might benefit from a little extra slide speed.

      • I recall a locking system called the “Blish lock”. It was used on the Tommy gun until it was deemed superfluous, and uses a locking piece that mus t slide down a steep angle to release the bolt.

  5. I don’t understand the mechanism. Is a DE-accellerator not a more logical part than an accellerator as a means to dampen the force of the recoil?

  6. Unless I’m severely mistaken, an owner or observer of this firearm could probably determine the function of the gas lever by weighing the slide and the force of the action spring. From this point comparisons could be made with the same components of other existing 9×19 blowback firearms. Several rounds of the same brand and type of ammunition could be fired through each in order to observe differences in case deformation, for example. Taken together I think a pretty good idea could be reached of the likelihood of the BSW operating as a blowback or even accelerated blowback firearm.

    I’ve read that the slide on a Hi-Point C9 weighs a little more than a pound, at an overall similar weight I’m guessing the slide of a VP70 is right up there as well (and that’s with a stiff action spring). Presumably, if the weight of the slide and spring on the BSW are significantly less than either of the above mentioned known blowbacks, then the BSW should (from the looks of it) be operating successfully because it is using some sort of locking or delaying system. My guess is with Mu on this one.

    Ian, can you comment on your impression of the weight/resistance of these components? Or would an accelerator somehow overcome the pressure issue?

    • It’ll be thirty five years or so since I handled a VP70, and it was a huge thing, slide weight was definitely more into the SMG than in the pistol range.

      Incidentally, spring force does very little in terms of keeping the breech from opening, that is essentially down to the weight of the bolt or slide.

      Spring force does have a role in decelerating the bolt or slide after it has opened.

  7. As others here have stated, the system seems to be a gas-actuated delayed blowback relying on kinetic “adhesion” (the inability of metal surfaces to slide over each other instantly when subjected to sudden impulse force) to delay breech opening until pressures have dropped to a safe level in the chamber and barrel. In many respects, it parallels the action of the VG 1-5 carbine in objective, if not necessarily in operating pattern.

    The lever-piston arrangement seems to have been borrowed from John Browning’s 1897 pistol patent, and the Colt 1895 “Potato Digger” machine gun, also designed by Browning. Of course, these were true locked-breech weapons, as opposed to delayed-blowback types.

    The double-stack-to-single-feed magazine was typical of SMGs of the period, notably practically every German design up to MP38/40 and even the British Sten. And of course the P-35 High Power pistol. As for this one’s rather odd version, the Llama Omni 9mm automatic pistol of the 1970s used a very similar magazine design. IIRC, it wasn’t noted for reliable feeding.

    The double-action-only trigger system seems to be an analogue of that of the Czech Vz.38 service automatic in 9 x 17 SR (.380 ACP). It was noted for that same sort of long reset plus a notably heavy trigger pull. It’s worth noting that while the Wehrmacht took all the other Czech small-arms they could grab after the Annexation, the Vz.38 was foisted off on the local police in the occupied territories. The Wehrmacht (and SS) may have been fanatical, but they weren’t stupid.

    Ezell in Handguns of the World shows one of these pistols on p. 429 in the chapter on German handguns from 1894 to 1945. The left-side view shows the frame-mounted (1911-type) magazine catch, the frame-mounted (distinctly 1893 Borchardt-like) safety catch right behind it… and a very Walther P.38-like lever up on the left rear of the slide.

    Exactly what that lever is for is a pretty good question. I’m inclined to suspect a straight, single-purpose hammer drop to render the pistol safe after stripping and reassembly. It also might function as such to allow Condition Two carry without using the frame-mounted safety, but that seems superfluous on a DAO.

    In fact, I don’t see any real reason for it to be on the pistol. I couldn’t see if the one Ian was examining had such a slide-mounted lever. If it doesn’t, that could indicate that somebody else didn’t think it was needed, either. Or that it was added because someone else (like maybe the Heerswaffenamt) did think it ought to be there. Who knows?

    BTW, the one Ezell shows does not seem to have a serial number. Does this one?



    • Manual Safety on DAO is definitely superfluous; yet, when comes to military version, it appears over and over. Why is that?

      I applaud such solution as on SIG 320 where is omitted even usual passive trigger safety. Striker drop safety on partly pre-cocked gun is enough.

  8. This pistol reflecting the German genius , seems a sample of delayed blowback automatic. The gas actuated lever in front of the trigger guard, looks working as a pendula at instant of firing. It has a hook shaped cut in its front with a up and backward slope at the front and a small bevelled lug at the rear. Locking bar in front of muzzle section of slide, is located within this cut with its rear being in front of small bevelled lug and capable to ride over it with rather slow backward movement of slide which happens during manual traction. When the pistol is fired, instant muzzle rise gives lever a pendulum motion as contacting its up and backward sloped cut with the front of locking bar, and since its pitch being so acute for continuation of lever downward swing, its motion slows temporarily until gas pressure coming from the barrel gas port accelerates it. In short, big front slope works during firing and small bevelled lug works during manual traction.

  9. Are you guys sure the gas lever is there to “accelerate” the slide? If yes, from the (by the way excellent) explanation in the video I could not determine how that should work.

    My impression is that the flat stud near the front of the gas lever is intended to engage the crossbar near the front of the slide and -lock- the slide during the shot. When the bullet passes the hole in the barrel, the gas lever is blown downward, the stud on the gas lever gets out of contact with the crossbar in the slide, and the slide is blown backwards by the residual gas pressure.
    If my theory is right, there must have been an arrangement to pull down the gas lever before the slide could be manually retracted.

    Anyway, thanks a lot to all who make this video of an extremely rare pistol possible.

    • To me it seems plausible that it could be fully locked breech gun that unlocks as you describe. Whether it actually is, I am not totally convinced. The acceleration happens after the slide becomes unlocked. As the portion of the gas lever that makes contact withe barrel is driven downwards, the angled cam at its rear makes contact with the forward part of crossbar of the slide which drives it rearward. The portion of the gas lever I am talking about is the bit that appears triangular in profile at the very front, top of the lever.

  10. It seems to me that the “accelerating lever” could pose a problem when firing this pistol through a vehicle gun port, which I think at the time was considered a significant part of the pistol’s combat role. Might that have been a factor in this weapon’s rejection?

    • Probably. Although the reason for the P.38’s revolver-like barrel was that it would fit through a pistol port while a full-length slide might not. This problem was corrected on the PzkwIII and later tanks by making the ports big enough to accommodate the front sight assemble of the Erma MP38/40 SMG.

      That odd folding ‘bar’ under the barrel of the Erma SMG is actually a hook to keep the barrel from being pushed back through the port by recoil. 9mm slugs ricocheting off the inside walls of the turret are not a comfortable thing to have in your tank with you.

      Several Soviet handgun prototypes of the same period also have “revolver-like” barrels for the same reason. The 1939 Korovin, Voyevodin, and Tokarev prototypes all were to a proposal specifying the ability to be fired through a pistol port just like the 1895 Nagant revolver could be. Operation Barbarossa abruptly ended the project.



      • Can anyone think of a way to improve this design? I would suspect that it would fare badly in mud. If I could alter the design, I’d exchange the gas lever for a rotating locking piece close to the trigger guard such that there would be no chance for dust or dirt to foul up the works near the muzzle. Or do I have it backwards?

          • I see it as a sort of Volkspistol idea, and reckon it was originally conceived as locking mechanism which you had to manually disengage to rack the slide- But by the time they really needed Volkspistols, they’d moved on to using gas itself to retard the action, rather than it actuating a lever.

          • If you went with a manually operated lock, as alluded to elsewhere on this thread, you could construct a Vp using the Walther manufacturing method but using less metal for the slide, presumably the lever could be made structurally sound with less material than say an extra layer of weight for the slide, manually operating the lever wouldn’t matter for a Vp.

        • You might be able to make a pistol with a very low bore axis using this method “I’m saying the hypothetical locking method with the cut in the lever to engage the slide being shaped thus / towards the muzzle” if you attached the lever to the trigger guard. Imagine if the barrel protruded forward of the slide for the port, and you went for a sort of Steyr m40 ergonomic layout the barrel with the spring around it could run almost above the trigger. It would perhaps look odd, with limited practicality, and you would need to manually drop the lever to chamber a round but I bet it would be an accurate target pistol with the rear sight almost on top of your hand.

          • One of those “Race guns” in .38 Super, fixed barrel, lowest possible bore axis… You could put most of the slides mass on it’s sides, what’s not to like.

          • Locks open on an empty, closes automatically on reloading, save having to rack the slide and thus depress the lever again.

        • Also one example of Voyevodin automatic pistol was given as a gift for Stalin:

          (second photo from bottom), text on pistol:
          For Narkom of Defense of USSR
          comrade Stalin,
          [i can’t read this part] 1942.

          text on grip:

          (Narkom is abbreviation for народный комиссар mean People’s Comissar, equivalent of American Secretary)
          (IOZ is abbreviation for Ижевский оружейный завод i.e. Izhevsk plant, manufacturer of this firearm)

          • Reading in PV description:
            “Автоматика его работы была основана на принципе короткого хода ствола со ствольной коробкой.”

            …sounds understandable, but what was the actual lock-up? Tilting link, rotary bolt? It looks not bad and not that heavy either. Kind of Lahti-sh. It looks really beefy though.

  11. The gas actuated lever in front of the trigger guard is forced up to lockat the first recoil impulse just like the cocking lever on a Spanish JO. LO. AR Pistol. then unlocked like a Colt Potato digger. Is that it?

  12. This is weirdest of pistols I have seen yet. After seeing this none of what I thought of can stand term “unique”. :-))))

  13. BTW, the alleged competitor, being Walther P38, as much as it revealed a completely new way of pistol design, had also its share of snags. Most notable, of course as with its successor Beretta 92, the frame strength issue due to lock lever cuts. But, they solved it after all; as Germans usually do.

  14. Interesting design, the term “accelerator” I took to mean, it’s function was like that of the Pedersen pistols cartridge moving back- To start the rearward movement of the slide. But with the slide being able to move with the lever up, I thought well it would blowback anyway. You could imagine the lever as a lock, if the slide couldn’t move when said lever was up, but you’d need to drop the lever to chamber the first round. Hmmm, that Pedersen lark slows the slides rearward movement after initiating it’s movement as is my understanding. So given this lever can move downwards freely under light spring pressure, perhaps it is there to snag on the slide to slow it’s rearward momentum down. Thats why you can cock it without lowering the lever, the shaped surfaces on the slides bar thing that engages the levers lug enables it to snag momentarily providing more delay than via blowback in order the slide doesn’t need to be as heavy.

    Anyway it’s another method of locking/delaying afixed barrel pistol, oh… If you hold a pen between two fingers and tip one end down, the other end tips up, perhaps that end jams into the frame under the recoil spring in a manner which allows the slide to pass it in that position. Sort of a toggle, straight- Locked, tilted- Broken, so unlocked.

    • So the delay, the snag if you will, isn’t merely the resistance of the levers spring being overcome, it’s the tilty’ness of the bar out of the frame type thing.

      • If that’s the case then, the gas operation is redundant really. I mean, the lever would drop anyway. Odd design, I wonder if they tried to make a locking version originally somehow i.e. That was operated by gas, trying to figure out how you might do it while keeping to the same sort of configuration of a fixed barrel. Some sort of spring loaded sleeve, around the slide, that covered the end of the lever, gas exits the port pushing it foward therefore off the end of the lever allowing it to drop. Er… Locked because the slide sits in the levers lug, the lever being attached to the frame, and the lever can’t drop free of the slide at that point. On the return, hmmm… No that wouldn’t work, how would the sleeve slot over the lever again… Tap, tap, tappity tap… The sleeve is around the barrel which would protrude from beneath the slide by say an inch, no same problem, rotating sleeve- Cut for the lever, rotates around it “monkey tennis”

        • I mean, even as an “accelerator” it’s defunct, wouldn’t it just blowback in the current configuration i.e. The shape of the levers lug, and corresponding rounded lever engagement bar thing in the slide.

      • I think originally they shaped the cut out in the lever and corresponding slide piece to act as more of a lock with the lever having a stronger spring, and you had to depress the lever manually to rack the slide hence the gas port to drop the lever in this “locked” configuration to automatically drop the lever. But they dropped that idea, when they thought it would operatate as a blowback but with the snagging action acting to slow the slide down rather than using a heavier slide.

        • If you angled it, in the manner the author suggested / that way towards the muzzle, the rearward movement of the slide would pull the lever up towards the barrel not away from it therefore locking it… Maybe it worked, but having to depress the lever to rack the slide was deemed a tad bothersome, somewhat crude like.

  15. It’s a slide decelerator, during blowback operation. Originally it was a lock, you manually operated initially, that’s my 2 pence.

  16. I’ve always thought a .22lr Spencer might have a niche, said niche being- Before getting your children a lever action Henry, bit slower possibly safer as a consequence, given one has to cock the hammer manually, in regards the adverts, It’s hardly a bb gun.