I bought this mountaineer New in 9/9/16, tried sighting it in with numerous bullets, sabots and powder loads. It shot like a dog, to make a long story short I purchased another barrel for it from Knight. When setting it up on my gun, since I had not shot the old barrel very much, it didn’t occur to me to measure the Flash Hole. I transferred my bare primer breech plug from the old to the new barrel.

Since then I read a post where someone said that the bare primer breech plug would only last about 100 shots with BH-209.

Since I shoot 110 grains of BH-209 normally, I measured the breech plug flash hole and it was a loose #65 Drill (.035+) then I measured my new spare breech plug at a #68 Drill (.031). Since I am going to be sighting in the new barrel I didn’t want to take a chance. With the old plug being .004+ diameter oversize from a new breech plug flash hole, I installed the New breech plug in the new barrel.

My question is at what point is a flash hole in a knight mountaineer too large to accurately keep shooting?

I have different muzzleloaders, Thompson Center Encore Pro Hunter, Traditions Strikefire, CVA Accura V2 & LR, all have good to reasonable groups “and now the Mountaineer?” In the past I would measure the BP flash hole and record it by date and size of hole and then measure it occasionally, as it was a long time between changing of a breech plug, and a lot of shooting with the muzzleloaders I had, shot 110 grains of BH-209 quite a bit in all guns. Now here is the mountaineer breech plug that just can’t hold up, what are they made out of?