I have that rifle (Portugal) chambered in 30-06 in the Featherweight version. Mine averages app. 1.1" - 1.2" for five shot groups at 100 yards with handloads from the bench. The only thing I have ever done to this rifle is adjust the trigger. It is far from a target rifle, but it is a good hunting rifle. How large are the "poor" groups that your son has shot?