So far apparently both subsonic loadings have only been on display at a show of some kind. It appears that both calibers are displayed in both a brass cartridge case and bimetallic cartridge case.
7.62x54mmR shown and discussed here-
In the photo above it appears that the 4 cartridges on the right have bimetallic cases and 5 cartridges to the left have brass cases
.308 Winchester shown and discussed here:
NOTE the bimetallic cases on the left and brass cases on the right in the photo above.
I used the Google translator to translate the forum discussions but the translations are not that good, so any of the Forum members here that are fluent in Russian would you please take a look at these pages and add here any helpful information. THANKS!!!
PS: For information on SIBFIRE: New "SIBFIRE" logo and boxes of LVE (Novosibirsk, plant #188)