Jim, I think that tight breech plug is your powder and not the rifle. Years ago when I used T7, I would always give the breech plug a twist or two just to break up that crud ring that forms, probably because of the sugar base. I think that is an old problem that has been discussed alot when the powder was new.

Dont have a mountaineer, but I really love my Elite. Once I added the lehigh breech plug and Knights 250 red hots using bh209 it really gained in accuracy. About 1 1/2 at 150 yards and then with a high lung hold, another bullet dropped into the same group from 200 yards sitting postition. Made my day!