Building a Lahti L-39 Anti-Tank Rifle

Sons of Guns have blogged about rebuilding a Lahti L-39 Anti-Tank Rifle from a deactivated parts kit.

It was developed in Finland by Aimo Lahti around 1939 in response to the many doubts of the original idea of the 13 mm anti-tank machine gun. After testing, those boys found that the 20 mm offered better penetration than its anti-tank counterparts. It was put into action in several wars including World War II and the Winter War.

Nowadays, the de-militarized version of this big boy are pretty rare. When you are able to reactivate one, like we did, the value skyrockets. Which is why Flem’s welding was key to this project.

… Most of the ammo was from World War II–it was at least 60 years old–which meant we had a lot of problems with the cases breaking and sticking. The crew polished them as much as we could, but some of the odd ball manufactured cartridges didn’t cycle at all. We just used it as a single shot at that point.

The only way to make a 20mm cannon rifle more cool is to mount it on a truck, and thats just what they did 🙂

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.


  • Justin

    I really hate this show and what they do on it, however I like when they do rebuilds such as this. Infact if the show was all about rebuilds like this and not about all the other crap, I’d probably watch the show more. I find alot of their builds unoriginal and boring. They basically make copies of good ideas and make them worse. On top of that they mount everything onto saigas and ar-15s which is beyond boring.

    Like I said, if they did a whole show about building a firearm such as this and went into great detail about how they restored it and how hard it was, then it would be a good show.

  • Greetings from Texas,
    I saw this epsoide, the Lahti looked great. Also, I liked that they pointed out it was a destructive device.

    I would personally like to see more explaination of class three, SBR and AOW catagories. Example, the Desert Eagle the lady had the shoulder stock put on. Many of us know that she couldn’t take it home with her because it was now a short barrled rifle. The thing is a lot of their viewers don’t.

  • Kyle

    As long as they don’t add extraneous rails, plastic and electronic sights to it this may be the only Sons of Guns “Rebuild” I like. Hopefully they use this as an example of how to build and restore an old gun rather than butchering it

  • Zander

    one of the VERY few respectable things they’ve done on Son of Guns.

  • Rob

    When are they going to paint it black and add rails?

  • Dick

    I did the same thing with my lahti about two years ago, I shoot it off my pickup with the mount I have. I saw you were using reloads on the show using vulcn 20 reloads, the same round used in the lahti is used in my solothurn, just built better

  • scurvy

    What’s the difference between a rifle and cannon? Fixed emplacement?

  • Andrew Racek

    I’m surprised they didn’t turn it into a trainyard with rails and that they didn’t add internal supressors.

  • I do love that show. The goofball who has the hots for the daughter and that entire “Made for TV” romantic tension part of the show needs to spend more time on the editing room floor tho.

  • Flounder

    Too bad their still DD’s. I think but just a thought. Oh steve you should find some figures comparing the Lahti 20mm round to our 20mm vulcan shell. ya know muzzle velocity, energy, bullet weight.

  • Firing one from its cute little skis is not a shoulder breaking moment. It’s like 10ga magnum. Well worth the $75 per shot the nice guy at the MG shoot was charging.

  • D

    I’m disappointed to even see Sons of Guns mentioned on here. Come on, nothing about Sons of Guns is cool.

  • Brian P.

    O.O …. I NEED this!

  • Chairman Mow

    Needs more:

    Hand drilled holes
    Black spray paint
    Poorly mounted Saiga shotgun underneath

  • Lance

    Looks fun till you need to pay for ammo!!! Steve buy the man some ammo?

  • Doug

    I dont care what you think about the show, that is cool!

  • howlingcoyote

    Hey, just the rifle to hunt wild hogs with in Texas!
    Where’s the laser sight? (Just kidding.)

  • CSA

    the show may have it’s faults,
    but at least common sense dictated the
    barrel and receiver to be ultra-sounded.
    they did find an area of non-fusion (welding error)
    on the receiver, that could have been disastrous.

  • Gir6543

    did they switch it out with an m9 pistol right before they shot? they’ve been known to do that

  • Big Jay

    I’ve had the unique pleasure of firing a Lahti before. Its a big kick, but a slow kick, and the shoulder pad covers a lot of area. It’s not nearly as punishing as some other “off the rack” guns like the Ruger #1 in .470 Nitro, the CZ 550 in 505 Gibbs, or the (worst of the group) Weatherby Mark V in .460 Wby Mag. The .460 will do as much damage to the shooter as it does to the target. But I digress…

    I will have to jump on the bandwagon of hating this show. But what they showed on this episode takes the cake in terms of stupid + dangerous.

    I am not a gunsmith, but I am a metallurgist. And there is NO WAY that I am trusting my life behind a 60+ year old, 20mm anti-tank rifle made from a parts kit with a welded reciever. “We checked the temper” – HA! Weld, cut through the weld, then re-weld. That whole thing needed a full furnace heat treatement, at least. Better yet, I would spec out the old reciever and have a new one milled by a machinist. Yes, I know that constitutes manufacturing a destructive device. But they have a licence to do just that.

  • The Lahti is cool until you have to regester it. Price DD papers. If you can aford that you don’t care about $75.00 or $100.00 per round ammo.

    • Earnán

      A Destructive Device tax stamp is $200, just like any machine gun, short-barrel shotgun or sound suppressor.

      The SOT and FFL to manufacture one are what is expensive, and Red Jacket already has those.

  • Glenn

    Glad yall liked it it was fun to build. I like doing the builds like this the most as I kinda feel Im bringing back history.
    Although I must say that first shot really had the pucker factor go up for me. I knew it would hold but there is always something in the back of your head, you know?

  • Billy Bones

    Sons of Guns is a disgrace to the firearms community.
    I was shocked to see it posted here.

    Frankly, if the show was more like the armor fighting vehicle restoration show, it’d be a winner.

    Gunplumbers 🙁

  • cy

    that gun, cool. sons of guns,… NOT cool. They make gun owners and firearm fans look like idiots. Surprised they did’nt mount an AK type on top and call it a Game Changer.

  • Chach

    This is gunna open up a whole new market.

  • I watch the show regularly thanks to TIVO, as an ex-FFL holder and gunsmith I have to say there could be alot more time devoted to explaining the laws and WHY you cannot do what they do at home. I ‘could’ do most of what they do at home if I wanted to risk a change of address to the Grey Bar Hotel!

    The first season was better so far than this current one IMO, the latest episode (12 Ga Gatling Gun one) was interesting in the fact that it showed what an error in design can cause (Just think if some home ‘smith trying that out while standing behind it!) and an insight into an R&D project is like.
    I hope they continue it in the future episodes, it would be awesome to see a belt fed 12 ga Gatling in a future episode. Not 3 Siagas welded together…..

    The Personal Drama crap needs majorly downplayed before the series devolves into “Gunshop Survivor” though. Just wasted time IMO. Also think telling an employee to chose between his job or would-be girlfriend is being a jack-ass, if not outright illegal.

  • drewogatory

    Thunderbolt says it should have been an Oerlikon 😉

  • This is just a cool as hell gun. The only complaint with this crew is that when they made this “gatling gun” shotgun. I really didn’t like the way the entire contraption rotated so fast that it looks like the magazines would fall off. Other than that I really like the work done by the Red Jacket crew.

  • Bamagerb

    What’s with all the negativity!!! Guns are cool, even if you don’t care for rails , lights,lazers or black rattle can finishes, and the general public needs a show like this to show them in a positive light.
    Just the fact that the show is on is a huge break through.
    Let’s lift the show up! Don’t be jealous of ” red jacket ” !
    The haters need a dose of humility and to think about the show in the light of our anti-gun media and public!
    Build what sells, keep making episodes, restore, rail, build, and paint it black! I’ll watch cause I like guns even ones I wouldn’t buy or could not afford.

  • best episodes are the rebuilds like the flame thrower, mg-42 and lehti

  • Shane

    I HATE this show and everything they do. They give gun owners a bad name and make all people who live in the south look like idiots. Nothing but contrived BS.

    Please don’t post anymore about Suns of Guns as I normally enjoy coming to this site but not today.

  • Logan

    I agree Sons of Guns=Poor machinist, Decent gunsmiths, stolen ideas (flashlight gun) way way too many segas. But still entertaining to watch.

  • Timppa

    Show might not be cool but good old elephant gun is über cool 🙂

  • Sandwichy

    Firing the MAC-10 blank pistol at his staff really pissed me off. I hope that was editing but it’s still a poor example to set. Also, was anyone else gagging when they chopped up that Browning machine gun for the SWAT guy’s shoot? I was pretty impressed with the guy who showed up to the interview with a rebuilt mg42. I think the show would be cooler in an Overhaulin’ format. I bet the guys at Mythbusters have a good collection, they’re always using Sig and Hk for their experiments.

  • Netforce

    I once caught an episode where the team modified a good ol’ Thompson machine gun into something of a modern machine gun. Since then I stopped watching. Doing something like that to a classic gun is just blasphemy.

  • Flounder

    Personally I liked the thompson modernization. Mostly because they took a semi and turned it into full auto. Yes they do do utterly ridiculous stuff and are incredibly lacking in originality. The Mac 10 folding flashlight gun was HORRIBLE great idea that they turned into a block of steel… literally! They even started with an airsoft version of magpuls design!!!!! I cried at that point. But every once in a while they come up with something awesome. This is one of those somethings.

    PS It is a reality show so they obviously do a lot of editing/ setting up things that aren’t really there. Just so they can get the “drama”. yes it is stupid but They probably are making A LOT of money from the show.

    I kinda wanted to see them shoot arrows from the judge. 😀

  • John N

    The American Chopper of the custom firearms industry.. sure, neither stop anyone doing something more innovative than painting some flames on a ugly ‘custom-made’ tank pulled off the shelves, or taking a super-rare can of matt black spray paint to a 1 in a hundred thousand Saiga-12- but hey, doesn’t mean they need to get any viewing numbers from decent people.

  • abc123

    “I’m disappointed to even see Sons of Guns mentioned on here. Come on, nothing about Sons of Guns is cool.”

    I agree, watch this clip:

    Remember that “DB” stands for douchebag.

  • william weise

    the things that i’v seen you band your crew do are rad sometimes a little nuts but for the better part of every thing they show us ya seem to all work together and i like team work . keep up the awsum builds may be tun down the flame throwers #1 COOL #2 INSANE TO THE MAX.I HAVE THE SAME RESPECT FOR FIRE AS YOU SO I KNOW WHAT YA MEAN! P.S MY SPELLING SUCKS AT TIMES…LOL HELL SPELL CHECK CANT EVEN FIGURE IT OUT