Ideas for subsonic 7.62x39?

[Lone Star]

I would strongly recommend against using fillers in any semi-auto cartridge. The violent action of these arms can cause the filler to shift with potentially disasterous effects. With the powders recommended, particularly the handgun and flake shotgun powders, no filler is needed particuilarly since the long 220-grain bullet must be deeply inserted into the case, safely taking up plenty of space without a filler. I've shot many sub-sonic loads out of my .30 Herrett (limited to 150-grain flat based bullets due to its slow 14" twist) using BlueDot with no filler and great performance. The Herrett has a very similar case capacity to the AK round.

Fillers are seldom recommended for any reduced loads anymore due to the potential for chamber ringing and filler shifting. Lyman, who for decades recommeded fillers in larger cases like the .45-70, no longer does so.

More .300 data:
http://www.accuratereloading.com/300whisper.html