Soviet "BO" cartridge?

In the back of Chumak’s book on pages 184 and 185 there is a timeline. In the section for Novosibirsk/#188 there is brass cased cartridge numbered “25” shown in production from 1960 to 1965(?). The notes at the margin simply say 7.62 “BO”. I suspect this is a sporting or match cartridge of some type, but would like to get a confirmation and find out what “BO” stands for if possible. I believe I have one of these (actually belongs to Hendere) dated 1967. Thanks for any help.

i suppose it’s “БО” - “Бегущий Олень”, Running Deer in English
sort of competition shooting back then

Very interesting! Thanks! I was pretty sure it was some type of match or competition ammo. According to the time line it seems to have been replaced by a similar load in 6.5mm. I’ve heard of this, but it’s out of my area of interest so I don’t know much about it other than it was used for competition in specially made rifles.

The 6.5mm is a necked down 7.62x54R.