Cartridge 6x39 urss?

i bought one cartridge under the label “5.6x39” but this cartridge is not the 5.6 because the bullet is an 6mm
the copper washed case is the 7.62x39 necked out 6mm
headstamp: 270 A

do you know this cartridge ? military or civilian ?

sorry for the bad quality of picture
6x39 (left) and 6.5 grendel (right)

In the book Les Cartouches pour Fusils & Mitrailleuses by Jean Huon (Second edition, page 413) there is a picture of a 6mm x 39 noted as a prototype from South Africa

The ECRA data CD lists this round also and the 2 headstamps shown are 270 A (I think it’s a russian symbol that looks like the letter A)

yes the letter “A” is a symbol in cyrilic

It seems you have a South African Military prototype, nice find.

The Cyrillic letter that somewhat resembles the letter “A” is actually the letter-sound “D” in the Cyrillic alphabet. It is the letter-code date-designator representing the year 1953. The code “270” is the factory-desginator representing what is today the Lugansk Cartridge Works, in Lugansk, Ukraine. They have used the “270” code on their headstamps at least as late as the year 2006, by the way.

This 6x39 is a South African development form about 1974 when a small caliber cartridge was evaluated for service. It was tested with several Musgrave projectiles. Will Reuter wrote an article about it.