I am really curious what CFE BLK will do in my 7.62x40WT, are you loading full case at 100%? How many grains do you load? This powder does amazing things for my 221 fireball, it's 30% smaller cartridge (21gr vs. 31gr capacity) than 223 but I chronographed my 50gr bullet avg 3348fps with 6fps spread and I got sum moa group. The powder really shines when at 100% or slightly compressed, I wasn't sure it it would be pressure safe for my cartridge but if you're shooting this from 7.62x39 which has greater capacity than a lesser capacity 7.6x40WT should be fine too.