I purchased a 20 ga. Mossberg 500 Super Bantam for my sons as a starter shotgun. The combo means it included both a rifled slug and shot barrels. The shot barrel patterns consistently very high and to the right, 15" @30 yds., using aftermarket fiber optic sights, Mossberg chokes, third party turkey chokes, and several types of ammo. The rifled barrel shoots sabot slugs dead on at 50 yards with the adjustable sights centered on the barrel. I phoned Mossberg and talked it over with the customer service representative and he though the shot barrel was threaded off axis for choke tubes and told me to send the barrel in for evaluation. I did so and will let you know what Mossberg says.