I'm just concerned about my ability to turn the plug past this point with only a moderate amount of force on a 12" wrench.
If you can go past the witness mark to another flat, the lug is bottomed out at the next flat, not at the witness mark flat. If it were bottomed out at the wittness mark, it would stop there. Thus the plug cannot be fully seated if it turns past it.
On all of mine I have to use a wrench when I get to the last two flats & that last 1/2 flat is very tight & I have to force it to the wittness mark, it don't just go there. And I don't go past that mark either, as once ya do, you just made a new seat past where ya were & there is no backing up.
Sounds to me like you need a new plug, but :hmm: I am not looking at it, something you must decide.
Oh, and I always use Neverseize on the breechplugs. Put it Inside the hole, not on the plug, or it will migrate to the outside edge & could cause a issue with browning it.