I don't recall the Brown Bear or the PPU cycling my KS-47 either.Russian Brown Bear 7.62x39 subsonic, 196 grain ammo will not cycle the action of my Mini Thirty nor KR-103.
Hornady has a subsonic 7.62x39 that claims it will work in semi-autos but I've not tried it; https://www.hornady.com/ammunition/rifle/7.62x39-255-gr-sub-x-subsonic#!/