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GM,
With all do respect!
I thought about what you guys said about my suggestion. It came to my mind that you guys might be thinking of a different situation.
So this afternoon I took a close up look at my CVA Optima V2 BH209 breech plug and its relationship to the barrel area where it sets installed.
As soon as I pulled the plug and took a look it was clear the breech plug doesn't seal off the front of edge. That surface on the inward edge of the plug isn't designed to seal. See below photo. It is a surface about 1/64 wide at the most.
Then I looked inside for a possible mating surface to seal from. There was none. That surface close to the plug's end is a beveled area to allow the gases to flow out of the barrel.
The surface that is designed to seal the breech is the plug's large flange that seats against the barrel's end. Only it doesn't do a good job. I used a piece of aluminum foil to put between that flange and the barrel to determined there is direct contact. When I screwed the plug against it the foil was trapped on one side but not on the other. In this case the surfaces aren't matched or square to each other.
In the photos comparing the surfaces on the end of the breech plug to the possible mating seal surfaces. There isn't one. The inward end of the breech plug set out an open space almost touching the beveled surface. The discolor ring on that beveled surface was were I pushed a 9/16" rod against it to see where it hit. 9/16" (0.562") is the internal diameter of the plug. The rod was a slip fit to the threads.
Therefore I will continue to use my plug tuning method to seal the breech plug. it works very good.
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