Lahti 20mm AT and other Finnish guns.

World War II Other Military Units
#1

The 20 mm Lahti L-39 antitank rifle:

The design and production of a domestic anti-tank rifle for the Finnish Army was delayed in the late 1930s by doubts and differences of opinion over which caliber to adopt. Initially a 13 mm caliber was the favorite alternative but in 1939 a decision was also reached to also construct two 20 mm weapons for tests in mid 1939.

The design work was given to Aimo Lahti who had two 20 mm prototypes produced during the
summer. They were then tested. Theoretically, the difference of muzzle velocity and penetration between the 13 mm and 20 mm wasn’t big, but the 20 mm round had superior fragmentation
effect when it penetrated the armor.

[LEFT][/LEFT]

[LEFT]On August 11th 1939, the L-39 performed well, fulfilling all requirements, and on the basis of these superior results the 20 mm weapon was selected and further development of the 13 mm rifle was
dropped.
On September 6th, 1939, General Heinrichs finally proposed that the production of this good weapon should start immediately.[/LEFT]

[LEFT]Before the production of the weapon was started, the Winter War broke out, as the Soviet Red Army attacked on November 30th, 1939. The two L-39 prototypes were first used on the Isthmus front*, near the Lake Ladoga. The weapons were issued to the AT-platoon of JR 28, and the platoon was subordinate to Os.Metsäpirtti (detachment Metsäpirtti), which was part of the delaying / covering troops of the Rautu (R-) group. The two prototype weapons were used with great success against the light Soviet tanks, and the weapon was reported to be effective at ranges of up to 400 metres[/LEFT]

[LEFT]* Source “Marskin Panssarintuhoajat” by E.Käkelä. Some other sources say that they were used in Ladoga Karelia 2 men were required to carry this weapon off road. During winter, a sledge was used, and on road marches a vehicle was used if available.[/LEFT]

After the Winter War

Later on, the L-39 received improvements e.g. night sights, AA-sights and a targeting scope.
In the attack phase in 1941 the 20 mm round proved to be too weak against most types of tanks. As the L-39 proved to be a very accurate weapon it was often used to destroy enemy gun positions, mg-nests etc. at long range.
Beginning on 1944, the L-39 was also used against the armored ground attack planes. A new pillar mount was designed and the rifle was fitted with extra recoil spring and a fixed striker for full automatic operation. This full automatic AA-weapon was designated as L-39/44.

http://www.winterwar.com/Weapons/FinAT/FINantitank2.htm#20

Aditional Pictures:

The member Tankgeezer with his Lahti L-39 ( you better dont fight with him)

#2

Very nifty post my friend! I am curious about one detail, the Lahti was chambered for 2 cartridges, the first a fairly short round, maybe 110-115 m.m.,(not particularily powerful) then it was rechambered for the far more potent 20x138 so my question is, which of the two rounds is reflected in this data? My thought is the earlier. Any ideas my friend?
:One thing I can say is that the German fellow in the photograph is about smack himself in the face with his left hand, the recoil is startling and forceful, but at least he doesnt have it in front of the trigger guard, (the empties fly straight down out of that area, very painful, ask my brother, he didnt listen):

#3

The data is for the german caliber 20x138B, fiirst introduces in the 2 cm naval MG C 30 and german army Flak 30 in 1932.

I am pretty sure that it was the only caliber in wich this massive gun saw service.

Video: explosive ammo vs steel plate

http://www.youtube.com/watch?v=bO0xRZWtRjM

#4

I was told that the rifle was chambered in a 20x113mm L-34 and i must qualify that as being the information I was given long ago when I first bought mine, so it being heresay, could be in error. There is a round of L-34 in the pic posted by Tony Williams, which i will attach here. its second from the left end of the line, so at least you can see what it looked like.Once the new cartridge was adopted,the designation was changed to L-39 (if what I was told was true) I felt the data was for the older round because the 20x138 seems to have better performance than the tables describe. It would be nice to be able to go to a range with some real armor, and see for myself, but there are no ranges large enough around here to fire it on. Those are some awesome videos, and the strike on the plate is just how it looked when I shot a 50mm plate at a few hundred yds/mtr. and I remember my ears ringing for awhile too. We had to place some plywood under the flash hider, as the muzzle blast would dig a hole in the ground and spray dirt and gravel in the shooter’s face (stings) :slight_smile:

20mm2.jpg

#5

L-34 ?.. hmmm, I know that there was a 20 mm full automatic cannon made by Lahti for aircraft use but is the first time I see this cartrigde.

As the chief indian indian in “Dance with Wolves” said:

“we need to tal more about it” and we need more info too. :smiley:

L-39/44 full auto AAA variant of the L-39.

#6

If you go to the post about the Japanese type 98 gun I posted the pics about, Tony williams posted the pic of those different cartridges, and the second left is captioned as Lahti L-34 that part didnt show in the pic I posted above. Perhaps our Mr. Williams can shed some light on this question.

#7

Your information is correct, look what I ve found:

Finnish use: Only two prototypes chambered to 20-mm ammunition of Lahti’s own design used in Winter War. During Continuation War L-39 saw large scale use (1.850 made) in hands of Finnish troops. With large variety of ammunition the weapon proved to be very versatile, so it remained useful even when its best days as antitank-weapon were gone. These new uses included bunker busting, long range sniping and use as improvised anti-aircraft weapon.
(*) Two prototypes of this at-rifle were manufactured in 20 mm x 113 Lahti calibre. They were used in Battle during Winter War and managed to destroy four Soviet tanks.

http://www.jaegerplatoon.net/AT_RIFLES1.htm

Considering the main AFV of the soviet invassion army, the T-26, with a maximum 16 mm armor is also possible that the claimed tanks are correct.

#8

I found this page that is pure gold, some information about the L-39:

That Lahti article on the Finnish questions & answers column was not an article but a collection of old surplus drawings (see dates of the signatures) with somewhat expanded captions. The whole story re special cartridges of Lahti anti-tank rifle was published in an abortive Finnish magazine “Asemaailma” (“Weaponry World”). I found that odds & ends material by a lucky accident from my home archives. Now I am seeking that issue of Asemaailma, containing that story and other drawings & photographs with an intention to translate it into English - if I shall get some time for this project. This a-t rifle on the photographs is property of a Finnish gun collector. It is de-activated. All the equipments are of original issue and standard.

These rifles were used during 1941-44 Russo-Finnish war for sniping and counter-sniping. The accurate and effective range was twice as long as that of 7.62 mm sniping rifle, despite of fact that Russian snipers could shoot at ca. 900 yards. Finnish countersnipers shot with high-explosive (T.N.T.-filled) shells to almost 2000 yards ranges… It was also amusing to set the forest on fire with the red incendiary shells to range 7000 yds + behind Russian lines. (That war was immobile trench warfare since the end of year 1941 until the June 1944). Sight was not needed, but just an improvized quadrant for the barrel elevation +32 degrees of angle to get the maximum range. Sensitive point-impact fuzes exploded those phosphorus-filled shells on the tree branches or twigs. The tree-top fire was very difficult to control and extinguish…

All the fuzes were made in Finland but those Duplex boosters were swapped with Suomi submachine guns from Germany. Duplex booster was needed to shatter the phosphorus-filled shell and splash the burning phosphorus all over. Those improved fuzes were ultra-sensitive. Use of them was prohibited in rainy days, because the raindrops could cause prematures… Otherwise was the TIKKA Ti 15/18 fuze safe to use, handle and transport but still among the most reliably functioning fuzes for the 20 mm shells during II World War: The best one.

That blue projectile was a solid shot of hardened steel, able to penetrate obsolescent Russian tank’s or armored car’s side or back armor plates. Even the heavy main battle-tanks T-34 and Klim Voroshilov were possible to immobilize with ten shots on the track link, or the turret was “riveted” with these blue bullets aimed into the seam between tank hull and turret. Some extra “rivets” could prevent elevation of the turret cannon.When the Russian tank crew tried to traverse that riveted turret, some brave Finnish warrior slipped ten or twelve pounds charge of T.N.T. below the tank’s belly and pulled the string of 5½ seconds time fuze. The dose was sufficient to kill the crew, but the tank was many times repaired for use of Finns.

Russian IL-2 land-strafing aeroplanes were heavily armored “flying tanks”, impossible to destruct with usual infantry firearms and too swift to get down with anti-aircraft artillery. An anti-tank rifle, mounted with a “Christmas tree fastening” on the tree stump 5½ feet high was flexible enough for dropping of these “Stormovik” planes.

It was usual trick to remove the sear of L-39 and use the handle of action hold-open lever as a trigger. The rifle shot full-auto fire, when the sear was removed, with a cyclic rate ca. 400 rounds per minute. If the incendiary shells with a tracer were available, they were loaded into the magazine alternately with blue AP bullets, but the penetrating bullets only could also destruct the Flying Tank.

Pilots of these planes were foolhardy kids from Comsomol; not the experienced fighter pilots needed for the dogfights against Germans in the cockpits of “Shylock’s presents”, Airacobra and Mustang fighter planes - donated by U.S. Government to Stalin. Excessive trust in armor plating of Stormovik planes was fatal to many pilots. Sometimes was the shooting range about similar to that of duck-hunting with a shotgun. Many times the pilot was killed in action with a direct hit through the cockpit.

Evolution of the Norsupyssy (“Elephant Gun” in Finnish) was continued still after the WW II, presumably until early sixties, because a tree-mounted 20 x 138 mm gun, able to shoot burst fire, was considered to be an ideal weapon against helicopters. Last guns produced were equipped with a fire selector. Full-auto shooting was, however, too stressing. Receivers of these anti-helicopter guns disintegrated, when the riveted construction failed, and there was not enough grants made for re-design of receiver to become burst-fire proof.

These three Finnish rounds of ammo were designed especially for L-39 rifles. (A fact unknown abroad and less-known in Finland too). All kinds of 20 x 138 mm Solothurn Long cartridges were possible to shoot from “Elephant Gun”, but with somewhat less accuracy. German, Italian and Swiss ammo were imported plentily during 1941 - 44 war.

http://guns.connect.fi/gow/QA2.html

#9

Wow my friend, you have been busy! a magnum of amontillado for you! I had figured that most of the more arcane information on all of these fine old guns had been lost to history. Its nice to see that isnt so. You should get the Indiana Jones medal for research ! Very well done! I’ll be reading this a few times so I dont forget it. Thanks man.

#10

You should get the Indiana Jones medal for research !

Thanks very much my friend but the main researchers are those finnish writers, the page is a fest for all the firearms lovers, they even tell you ho to handload the Lahti ammo, for…subsonic shooting… amazing :shock:

#11

That is amazing. RCBS company out west makes dies for the L-39 cartridge, and there are a number of suppliers for projos. (even reworked U.S. 20 mm will do, the driving band is a little thicker on the U.S., so it needs to be turned down .010" or so. The propellant charge is sewn into a silk hose bag, and a 10 grain black powder initiator charge is sewn to the bottom of that. If I remember right, the powder charge is around 495 grains of a powder we dont use here, but there is an equivalent powder.
The main problem is that when the thing fires, and extracts the empty, it really pulls hard on the rim, usually deforming it. sometimes making it unusable for further loading. the gas is adjustable, and so many will turn it down to the point it becomes a manual gun, to save the wear on the cases. There is a company that makes new ammo, the case is of stainless, and the price is 50-60 USD. per round.

#12

A bit pricey :), but you are shooting a big piece of story there.

#13

Chinn describes the Lahti 20mm aircraft gun in some detail and implies that it was used in service, but in Lahti’s own autobiography contradicts this: he made four different 20mm automatic cannon, all of which he considered to be failures. Only one seems to have seen (very limited) service in patrol boats, as described in the “updates to Rapid Fire” page on my website:

“Some more information about the Lahti L-34 “boat gun”. Ten of these guns were ordered by the Finnish Coast Guard (Merivartiosto) for use in the new VMV patrol boats (although most of these boats carried the 20mm Madsen instead). They were manufactured by VKT (Tampella). There was an experimental wheeled mounting but the service weapons had a simple pillar mounting. When firing AP shot penetration was 30mm/300m/90 degrees or around 20mm/300m/60 degrees. Some more data has emerged on the L-34: the gun was available with a magazine feed (15-round box or 30-round drum) or with a belt feed. Gun weight was 60 kg with mag feed, 69 kg with belt feed. Rate of fire was 325-360 rpm and it had a maximum range of 8,000m, with a maximum elevation of 6,900m. Three different projectiles were available, all weighing 136g: an AP-T, and HE and an HE with an extra-sensitive fuze. Cartridge weight was 275g and the muzzle velocity 800 m/s.”

I have a French sales catalogue for this gun. It is on my list of tasks to translate and post this on my website. Incidentally, while the 20x113 ammo was used, various others were tried including a version with a belted case.

#14

Chinn describes the Lahti 20mm aircraft gun in some detail and implies that it was used in service, but in Lahti’s own autobiography contradicts this: he made four different 20mm automatic cannon, all of which he considered to be failures.

I can tell you very confidently that the quote above is 100 % correct, The Finnish Air Force never used the Lahti gun. Alll were foreign designs like the MG 151 Mauser and others ( I believe they put a madsen gun in a experimental fighter)

#15

This is getting juicy,I am glad to have my piece of history, and fortunate it is in such good condition. The only thing I am missing is the spare parts kit, I have the cleaning kit, and magazines/cases. (and a goodly box of ammo,even a bit of the German stuff W/ the waffenamp stamp on the projos.)
It would be nice to see some of the other makers guns, the Madsen, in particular, but the only ones i’ve seen here are the L-39, the Solothurn,some oerlikons,and a fair number of .55 Boys, even a couple of PTRS guns.

#16

If you mean other anti-tank rifles, well here’s a list of those which saw service, with their nationailities and cartridges (from a table in my book [b]Rapid Fire: the Development of Automatic Cannon, Heavy Machine Guns and their Ammunition for Armies, Navies and Air Forces[/b]:

PzB 38 D 7.92x94
PzB 39 D 7.92x94
7.92mm M.SS 41 CZ/D 7.92x94
Maroszek P 7.92x107
Sholoklov SU 12.7x108
Mauser M1918 D 13x92SR
.55" Boys Rifle UK 13.9x99B
PTRS SU 14.5x114
PTRD SU 14.5x114
15mm MPzB M41 CZ 15x104
Oerlikon SSG CH 20x72RB
Oerlikon SSG 36 CH 20x110RB
Solothurn S18-100 CH 20x105B
Madsen AT DK 20x120
Type 97 J 20x125
Solothurn S18.1000/1100 CH 20x138B
Lahti L39 SF 20x138B
Bofors m/40 S 20x145R
Carl Gustav m/42 S 20x180R
Tankbüsche 41 CH 24x138

I should note that the Madsen and the Bofors were really automatic cannon on low-angle mountings for AT work, rather than rifles. The Swiss Tb.41 was half-way to being an artillery piece, and had a wheeled mount. The Carl Gustav m/42 was recoilless.

#17

Hi Tony, I thought you would have something pretty interesting to add, I just bought a copy of your book too. So I’m looking forward to reading it.
I have seen examples of many of the guns you listed, though sad to say the more part were in museum settings.(better fun to see them actually firing) The pieces I spoke of earlier were the guns owned by folks in my home state (Wisconsin) There is paperwork needed to move an N.F.A. weapon across state lines, so I just get to see the ones owned here. Thanks again!

#18

If you found a copy of Rapid Fire you did well - the publisher has sold out, and no more are to be had.

Don’t forget to check the Rapid Fire Updates page on my website, which is changed from time to time.

#19

I found a used copy on Amazon, it’ll be here in a few days.

#20

Images of the Lahti 20 mm full auto cannon Chinn stated in his books that the Lahti was an inpiration for the Berezin Ub and B-20, however knowing the extremely reduced number of Lahti guns made this sounds very unlikely.

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