one thing a rifleman must relize is your not going to get those 1/4 inch groups at 100 yards with a smooth bore shotgun.but then again you don't need 1/4 inch groups to get the job done.if you take a 9 inch pie plate(about the same size as a deers kill zone)and from a good bench rest put 5 slugs on that pie plate at 100 yards,your ready to go.100 yards or a touch more will or should be your max range with a smooth bore.its important that you try as many different brand slugs as you can find or afford.you will be amazed at how differently each manufactorers slug will shoot from your gun.im going to agree with indyhunter about the 3 inch slugs but if thats what shoots concistanly out of your smooth bore then by all means shoot them.to start out try the 2 3/4 inch slugs in 1 oz and 1 1/4 oz wieghts all the companys make them,remington-winchester-federal-active-brennekee and so on.try them all if you can.realisticly speaking,any where from two to five inch groups are the norm.group size is a direct result of the amount of testing you do.so again,shoot them all if you can.