found the russian website with the pics of the NK 8,2x66SR Mosin hunting rifle
http://www.maksimov.su/in.php?tnum=1&...-8.2/nk-8.2.htm

we have to thank this gentleman for the excellent pics showing this forgotten hunting rifle in every detail

why such a big case and only a muzzle velocity of 440-450 m/sec ... well its blackpowder ballitic. when we remember that russia was a communist dictatorship in 1931 its surprising they sold black powder to hunter for reloading ammo BUT only blackpowder. so the 8,2x66 Semi Rimmed was big as possible for a maximum BP load but fits into the Mosin action and and the rifle cant be shot with russian service cartridges. up to the 1950s only blackpowder was available for the russian hunter but later they got also Nitro shotgun powder.

http://municion.org/

I would say the best basic brass to make this case is 6,5x68R