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20 X 113 Lathi


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Premium Member
Developed around about 1930 by the Finnish arms designer A. J Lathi there were 2 versions produced, the aircraft cannon and the anti aircraft cannon.

Cases were made by the TIKKAKOSKI plant. Before 1940 the name appears in full on the headstamp, post 1940 specimens (as in the photo) only have "T".

The colouring of the projectile is a mystery, the book I have on this states:
"in the United States practice cartridges have been round painted in lead red, it is supposed that these are not original Finnish specimen".
The one in the photo is painted in this way, has anyone any idea why?

All INERT/hole in back & primer oiled etc.



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One quibble - the spelling is Lahti (although it is often misspelt).

Bill Woodin has a wonderful collection of different Lahti rounds and cases, 20x113 belted and rimless plus some shorter cases. They were shown in a nice colour pic on the front of the ECRA Bulletin #514 about 18 months ago.

AFAIk the only gun to use the 20x113 round was the L34 "boat gun", used in very small numbers on patrol boats. Lahti did produce some experimental 20mm aircraft guns (four different models) but (contrary to Chinn) none made it into service. I'm not sure what ammo they used.

I have a French sales brochure on the boat gun - I keep meaning to translate it and put it on my website.
Thanks for the updateTony, I had a funny feeling that Lathi was spelt Lahti but went by the book I was looking at. At least I got TIKKAKOSKI correct.
I'll check out the ECRA picture, I seem to remember seeing it.

I have collected information about 20 mm Lahti experimental case types and have so far measurements of 7 different case types from 1934-38. Many of them were prototype aircraft guns.
The belted 113mm long case was not only for Tampella guns, but also for one prototype of aircraft gun. These cases were ordered from Kynoch as well. TonyE did for me some research at Kynoch archives, but unfortunately he passed away before the stuy was ready. Tampella made 2 prototype guns and they were used during WW2 at Tampella factory as AA-guns.