If you have not bought your gun yet then go ahead and buy one chambered for 3 1/2 in. THEN PATTERN YOUR GUN. You may discover that a 3 in load patterns better or a 3 1/2 load is better. Every shotgun that is chambered for 3 1/2 will also shoot 3 in. shells as well.

As most said they are not necessary especially if you are shooting ducks at 35 yards and under. With the introduction of hevi-shot a 3 in. will perform for you really well.

Nemont