FWIW, I use BH209 in a Knight Wolverine 209 using the red FPJ and I have had zero problems at the range and in the field with the rifle going off. What I have experienced, with a few shots is that with Winchester 209 shotgun primers, the primer lifts up and on even fewer occassions it sometimes comes out of the primer cup after the shot. It does not seem to act like a missle but you should be aware of it. I plan to try some Federal 209A shotgun primers during the winter to see if they act the same. I also have on order a Non-FPJ breech plug to try as well.
I have swapped the plunger and breech plug from the Wolverine 209 in to an MK-85 and they seem to fit fine, I have yet to fire the MK-85 with the Wolverine 209 ignition. That will probably be a winter project as well.