3 1/2" slugs are a waste of money and energy, the energy part being what happens to your upper body when you light one up! I really don't see why 3" slugs are even available, the gains in energy and especially in trajectory are very minimal. For example, a Winchester Partition Gold in 3" is about 1/2" different in trajectory at 200 yds than its 2 3/4" counterpart. Big deal. And at that distance still has loads of energy left. Don't get caught up in the "bigger is better" stuff.