I too would recommend the 5/32" flame channel, and thread it for a vent liner. I have some custom plugs with those measurements and a .242" - .243" diameter primer pocket with a flat bottom that have no blowback. If you want to get rid of the blowback in the Knights, you have to have all the right dimentions. I don't look like you are there yet. Put a liner in it, that way you can customize your flash hole without ruining your plug. The liners in my custom plugs are .031", and ignite BH209 with no blowback, even using heavy charges.
If he is going to make a FPJ plug, DO NOT use that heavy chamfer on the O.D. of that nipple like on the standard plug. All that does is splay out the FPJ and spew blowback all over. I know Knight put it there to aid in moving the FPJ into battery, but it doesn't really need it. The flame needs to be channeled into a larger diameter flame channel than the standard 1/8" that Knight uses, or the flame channel taken out of the equasion.
One thing is for certain, the .45's definitely have more pressure with the magnum loads that the .50's.
The primers should be slightly (.003"-.005") long before the bolt is cammed all the way down. This action will compress the rim of the primer, making the front seat up tight in the bottom of the primer pocket. Just a few of the things I have discovered in the quest to get rid of the blowback.
The standard NFPJ Knight plug also does not have a deep enough primer pocket, this allows the back part of the primer to swell and stick in the adapter when shooting mag loads. The very large diameter firing pin and firing pin hole in the bolt doesn't help matters, allowing soot to seep between the primer and battery cup.
Let us know when they get it figured out.
