Personally, After shooting all the BH209 that I have, its a head space problem where you lose to much of the primers gasses and the rifle misfires. I can take a factory cva plug, shim it or o ring the primer pocket and have zero trouble. Leave it in factory set up and you might experience a hang fire or complete misfire at times.
Just like with #11 caps and black powder subs. Vented nipples with those powders suck.