I had the same trouble with mine. I finally got it to shoot 2-3 inch groups at 100 yards off the bench. The problems I was having ranged from damp powder, to loose scopes.
Make sure everything is tight (scope), get some fresh powder (Im using 80g of Pyrodex 'P'), and make sure each load is seated with uniform pressure. Some guns like a fouled barrel for best accuracy.
If worse comes to worse, send it back to TC, and let them figure it out.
Good luck,
kb