Okay boys, i was playing around with breech plugs last night and this morning i got it perfect so far. Need some slight tuning but excellent thus far.
Using the breech plug out of my CVA Accura, it has been modified with a .035" flash hole, factory flash channel and the primer pocket was slightly drilled deeper and a rubber O ring added for head spacing adjustment in the Accura.
This breech plug is a direct replacement for the Hunterbolt! No mods needed. The O ring seals up tight when the firing pin hits the primer and holds it there perfectly tight up against it and thus eliminating blow back! This right now is probably about 95% blow back free and 110% reliable with Blackhorn209. I do have a little space that allows the primer to move back into the bolt about the thickness of a dime.
I am looking at a good way to adjust this thats reliable. My idea is to leave a little extra meat on it so it actually presses the primer into the O ring hard, making for an even better seal.