They are Winchester 209 Shotgun primers. They come out shiny so I don't have any blowback.
Breech plug hole: The main channel hole is not 1/8". When I clean with a drill, I am starting with 5/64" (.079) finish with a 3/32 (0.093"). It is dirty and takes some effort to twist with my fingers particularly when most of the way in near the ignition hole where there is some carbon.
7/64"(0.109") will not start. It is bigger than the original hole. The original passage hole is slightly larger than the 3/32 but not very much maybe a no. 40 drill (0.098") but I don't have a numbered drill set just a good fractional set. It is considerably smaller than 1/8"(0.125")
I don't have a wire gauge set or drills small enough to determine the size of the smaller ignition hole but I held the plug up to the light each shot and it looks clear.
Also, I am seating the bullet on the powder firmly and trying to be consistent.