Posting here cause this is the most recent discussion i saw of this load.
I bought a bunch of it with the intent of using them in a cz600 trail in 7.62x39 for a little compact suppressed fun thing.
Disappointingly i have found that out of the CZ600s 16inch barrel, the half of these rounds fired are clearly subsonic, a quarter just riding the edge of the sound barrier and a quarter sound really nice.
Given that the claimed test barrel is a 20in at 1050fps, i wonder if by 20in the projectile is slowing down...
Anyway, it was accurate enough. I will have to chrono it and try in an AK (maybe the gas port releases enough pressure to keep it subsonic) and then a 24in rpk to see if the projectile is actually slowing down.
From my previous messing around with brown bear subs, i found that they would usually stay subsonic in a 16in, but always were supersonic in the 24in unsurprisingly.