First of all, do you have a scope on it? if not forget shooting 100 yards and getting good groups. second of all, make damn sure that the barrel is screwed all the way in. i had the same problem at first because the nut wasnt tight. Thirdly, its gonna kick, i suggest getting a recoil pad. Forth on the list as far as i know, the only federals that shoot remotely like a bullet are the Barnes Expanders, possible to get 1" groups at 100 yards. Possible!!
this is gonna take time for you to get use to but once you do you'll be a crackshot. and when sighting in sometimes it is best to shot once and take a break. i find doing that and wearing hearing protection get me sighted in a whole lot faster.