I have a 58" Kodiak (muzzleloader) and it groups very well.
I change the back sight for a single express (hand made by me).
I do not know if every rifle groups but according to Pedersoli, they have to put every bullet into 15cm (6") at 50 meters.
This is one of my best groups (LR+LR) :

Martin

PD: I pulled one of the shots. BTW each square is 1,7" by side