this is just my opinion the breech plug holds the pressure upon firing yes thereis blowback into the primer hole but the thickness of the primer holder is thicker than the 2 thousands gap. you can only push so much through that small hole/ backpressure/ back when i built my first h7r 10 years ago with primers i didnt have these primer holders andhad the primersflush with the back end ofbreech.i just weht and measured my girlfrinds the 50 cal . bbl.was bought at a gun show without the action i also have that much clearance just almost 3. im not worried about it it shoots good locks up tight and shot 100 plus rds. with no problems at all.
