A heavy barrel should be accurate if it's internal dimensions are correct, but a sporter weight barrel need be no less so if made within the same tolerances, but it depends how you define accuracy. A hunting rifle should be able to place its first round very close if not right on the intended point of impact. A heavy barrel varmint or target rifle should be able to do so repeatedly over a long string of shots. This is not necessary with a big game rifle where the reason for shooting has been resolved with the first shot or two. The objective with the target rifle is consistently tiny groups as this provides a competitor his best chance of success. But in the field, armed with a big game rifle, a hunter's success is measured another way, where a rifle's reliability, handiness, and weight are all more important to the success of the endeavor than pin point accuracy. The hunter who can put his first round on target on demand, at an estimated range, and under a tight time constraint, chances are he has the correct rifle. If he is fatigued, and has difficulty holding his rifle up long enough to make the shot, he may have chosen poorly.