Sweden’s WWII cold weather pistol: The Lahti m/40

Swedish Pistol Lahti m-40 side

The Lahti pistol was the brainchild of Aimo Johannes Lahti, a Finnish soldier turned arms inventor. While there is some dispute it’s hard to ignore the fact that Lahti’s pistol uses a very similar locking block to the earlier Bergmann-Bayard pistols. The overall styling appears to have been taken from the German Luger, providing good handling and natural point of aim for then-standard one handed shooting. His pistol was adopted in Finland as the L-35 and when Sweden’s contract for the Walther P-38 was interrupted by WWII, they adopted the Lahti as the m/40. These were produced by Husqvarna Vapenfabriks through the war and a little beyond.  A little more about the history can be found at C&Rsenal, but let’s talk about its unusual action here.

Swedish Pistol Lahti m-40 sideby

The Lahti is a short recoil design with an inverted-U-shaped locking block set over the bolt and nested in the barrel extension. This locks the bolt to the barrel extension for a short distance during initial recoil. As both parts travel rearward lugs at the base of the locking block ride in channels in the frame. These direct the locking block upward, releasing the bolt to continue back further after the barrel extension is halted.  This feature can be seen, somewhat simplified, at the right side of the included animation.

Lahti was concerned about the semi-automatic action functioning in the extreme cold weather of Scandinavia. His fear was that the initial force of recoil would be used up in moving a frozen barrel extension, with not enough remaining to drive the bolt back. So he included an accelerator on the left side. This semi-circular “foot” is attached to the barrel extension and is struck against the frame when the extension is halted. This slams the other end of the accelerator into a notch in the bolt face, “kicking” it with some of the leftover energy of the collision.  We can see it working on the left side of the animation.

Swedish Pistol Lahti m-40 POVFinally, while we’re talking about the Lahti I should probably go on to say it is a pleasant gun to shoot.  Its heavy weight paired with the 9x19mm cartridge, steep grip angle, and prominent sights make it stand out against other pistols from the era.  If you ever have the opportunity please do try one out.

 

Related

Othais

Othais is practically useless with modern firearms. That’s OK though, because he specializes in Curio and Relic military pieces and has agreed to decorate The Firearm Blog with a little history. He maintains his own site, C&Rsenal, with the help of his friends and the collector community.


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  • strongarm

    Lahti’s accelerator not only quickens the breechbolt backward movement, but also slows
    the barrel extentions recoil speed since it works nearly in same manner with Kiraly’s lever
    delay. This ends a much quicker extraction and cocking speed than expected but in case
    of magazine follower upper rise being not able to match this speed, a feeding issue will
    occur.

    • dp

      Hi strong-arm; you have good and worthwhile observation. This ‘accelerator’ was an afterthought introduced little later in process. Also, it is believed that it was omitted in Swedish version. There was discussion on the subject at FW in past as you may know.
      BTW, I measured (close enough) the angle of grip – it measures at about 30deg – very steep with not that many similar designs, noted exception being Luger. One thing which I like about this gun is that it took the Bergmann-Bayard lock to its maximum potential. Aimo Lahti was beyond any doubt great designer.

      • strongarm

        Hi db, thanks for your interest. I think, Lahti’s accelerator was thougt
        simply to give speed for breechbolt opening but, residual momentum
        over the recoiling barrel extention would slow its motion, eventually
        creating an overfast breechbolt and,vıa weakened magazine and
        recoil spring, this would give, breechbolt override on the top round
        of magazine instead of driving into the chamber. This shoıuld be
        encountered in the times when that pistol used but, overspeeding of
        accelerator could not be understood. Accelerators in fact, are also
        balancers, they quicken some parts but slow others as engaged.

        • dp

          Yeah right, I call them privately “momentum convertors”. You are certainly aware that recoil operated guns who do not have them are in dis-advantage (such as original Johnson rifle). Most pistols do not even know if they need them or not; interesting. Take care!

  • hkryan

    More articles like this please! I’m liking the animation!

  • Steve (TFB Editor)

    I love the animation!

  • kipy

    It’s like a non-poopy Nambu

  • Rabies

    excellent article, thank you!

  • Bubba

    These pistols were pretty bad.

    At the time they were being produced there was a shortage of good quality steel, these pistols were made out of poor materials. And they were shoddily and haistily assembled because the Swedes were afraid that Hitler could invade at any time. This coupled with the fact that they were sometimes used with the unusually violent m/39b submachine gun ammo meant that they wore out quickly and often broke.

    So these pistols were taken out of service in the 80s and replaced with the old m/07 (colt 1903 clone) pistol for a couple years until the Swedes bought Glocks in 1988.

    • Sulaco

      True Bub, and If memory serves the accelerator if left fully functional in warmer weather caused some damage to the pistol in a fairly short period of time.

    • swede1986

      The post-war ones made for the Danish army were made from better quality steel, and weren’t generally as abused as the Swedish ones.

    • Leigh Rich

      The ones in question that crack were used by ther Army and were all destroyed.

  • SP mclaughlin

    I’d like a mocha Lahti…

  • dan citizen

    I had one of these twenty odd years ago, mine was exquisitely made, beautiful finish, tight tolerances. Mine liked hot ball ammo and was accurate enough.

    Most examples I have seen since were not as finely finished.

    I used mine as a “truck gun” and occasionally as my sidearm. I don’t recall why I sold it or for how much.

  • Rustan

    The Swedish m/40 isn’t an exact copy of the Finnish L-35 and it never was called “Lahti”. It’s heavier and had a reputation of being less reliable.
    Also it wasn’t exactly replaced by the FN 1903 m/07 as that was still actually the “real war” pistol and m/40 only used for peace time training. But yes, that meant it was in storage waiting for WWIII.

  • Lurgubbe

    http://www.gotavapen.se/gota/m40/pist40_1.htm

    Perhaps this link would be of interest.

  • Leigh Rich

    Mine is a M40 Lahtia. Made in Husgvarna Sweden then went to Denmark for the police after the WW2. (Has D in serial nr.)
    Mine is one of the desirable models for reliability and strngth. It Had seem all the good modifications .They are an amazing pistol and fun to research. I’ve got the the holster and accessories for mine. ..
    A must own gun for a collector. I am a collector of one of everything.

  • mikewest007

    Hmmm, I’m having that silly idea of photoshopping a Ruger Mk1 bull barrel on it.

    • Leigh Rich

      WHY?

      • mikewest007

        For the lulz, mostly. I once threw together bits and pieces of a Bergmann-Bayard, a Roth-Steyr and a grip from some early American revolver (can’t remember if it was S&W Model 3 or Colt SAA).

        And then there was that thing I put together from a Spanish full auto copy of a Mauser Broomhandle, MP40 and Tommygun.

        And a truly, truly bizarre mash-up of a Winchester M1907 rifle, M1 Carbine, M14 and Mini-14, topped with a completely unrelated Cutts compensator.

        • Leigh Rich

          Sorry I own real guns.

          • mikewest007

            Then ask real questions, not mumble “why” like a slobbering troglodyte.
            The amount of bureaucratic hoops one is forced to jump through in order to get a firearm permit over here and throw money at government drones who can and will tell you in the end that your application was rejected is terrifying. I really can’t do more than have fun with Photoshop.

          • Leigh Rich

            WHY?
            Sorry you live in such a restrictive and oppressive society.
            Seems to me the topic here is the Lahti pistol not photo shoping weird guns.

          • mikewest007

            Well, you asked why would I try and photoshop the Lahti into something weird, you got your answer.
            Also, don’t be surprised with a former communist country being “restrictive and oppressive”. It took them 23 years since communism fell to finally figure out that the gun laws might be a wee bit too restrictive. Paradoxically, I can go to a gun shop right now, buy any caplock gun, including Old West revolvers like Colt-Walker or Remington NMA, including modern replicas of those, no license, no permit, no questions asked. But if I wanted a Colt SAA, or a Lahti, or a Kongsberg Colt, I’d have to jump through hoops and hope that the local police commissioner knows and likes my mom or dad (both retired cops).

  • phuphuphnik

    I bought one of these just this month! I cannot wait to try it out. Sure is heavy, a little more than 2 kilos loaded.