7,62x39 formed from 7,62x45

Hey guys - I’ve had this one 7,62x39 in my collection for some years that has always looked kinda “off”. It’s kind of easy to tell why - the throat and its crimp looks very rough and irregular, and the rim and extractor groove is much thicker and longer than on regular 7,62x39.
From what I can tell this is very simply put a 7,62x45 that has been cut down and been through a 7,62x39 body size die.
See the pictures here…
Left-to-right bxn 7,62x39, the “mystery” round, bxn 7,62x45:

The headstamp of the round is “53 bxn I”.
The rim thickness and extractor groove length/angles is the same as on x45. As one can see the case is ever slightly so shorter than the factory x39.
Was this done in some sort of systematic effort, in Czechoslovakia or elsewhere, or is it possibly just some homemade reloading job/small-scale operation, to get use out of otherwise obsolete 7,62x45 ammo? I’d love to hear if there was any other known cases of this kind of case. Pun intended.

Ole

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May I add another question to this discussion? Why would one re-work 7.62x45 into a 7.62x39 when new AK ammo is cheap and widely available? While 7.62x45 is becoming to disappear.

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Large quantities of these turned up in Northern Ireland back in the 1980’s having been acquired by the IRA. My understanding is that they were reformed by an American company called Thunderbird Corporation.

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I don’t know where this specific round comes from (other than its Czechoslovak origin), but I am in Norway where neither 7,62x39 and 7,62x45 can be called normal shelf goods.

Ole

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Found this on AR15.com:

Those would have been reformed from 7.62x45mm. This was done on two separate occasions as far as I can tell. First was during the Vietnam War when the U.S. Army contracted to have a bunch of 7.62x45mm reformed into 7.62x39mm for training troops with captured AK-47s. This was done before Lake City began manufacturing 7.62x39mm for training use and aid to Cambodia. Second was sometime in the 1980’s for sale to the general public. I’m under the impression that both times the work was done by “Thunderbird Cartridge Corporation”. The Czechs. did not begin manufacturing 7.62x39mm until 1957.

Ole

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These reformed 7.62 x 45 case 7.62 x 39 mm rounds were available commercially for awhile in the USA. I don’t recall who made them, but “Thunderbird Cartridge Corporation,” mentioned above, rings a bell with me.

I think the motive was that a lot of the ammunition was brought in as MILSURP at a time when there were almost no rifles in that caliber in the USA. Converting the ammo to 7.62 x 39 mm was, commercially speaking, about the only way they could sell it.

John Moss

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Thanks to that conversion the price and availability of 7.62x45 in US was dramatically altered.

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Thank you all a lot for the replies :-)

Ole