Hello:
Guess we go over the fence once in a while. Have to confess I have been to Paree.
At the suggestion of AZ Trooper, earlier this year, I met with Bill McCarthy during the Fall, 2017 N-SSA Nationals. Bill's possible contact info is resmillwork@enter.net. We had a long, especially informative discussion about the First and Second Model REPRO's that he 100%, lock, stock and barrel, scratch builds. Both are N-SSA approved. They are drop-dead beautiful and shiveringly well made with extreme attention to proper materials and machining skills. And, they shoot, well!
Bill has adapted a successful French artillery semi-flexible breech seal (from polymer instead of more ancient materials) that expands under pressure. It is durable and easily replaced. No gas blow-by!
If you intend to shoot yours, it might be worthwhile to reach out to him. He uses paper cartridges in his repro's and achieves fine accuracy.
When you see one of his ....... !
All the best,
El Supremo/Kevin Tinny