I have a 42" Montana BBL, 40 cal, prb barrel, deep rifling,1-48", 1" cut for a false muzzle on a Billinghurst underhammer target rifle. It belonged to Bill Mowrey, he used a lot of them as I understand. You can see the faint felt tip markings on the bottom flat. They are highly regarded around here.
I plan on putting Lyman Receiver and globe front sights and snipe squirrels at a golf course.
The false muzzle didn't come with it..."sigh"