Sounds like you did not get the shoulder set back far enough, which means you need to lower your die.
Also, get a case gauge to check your rounds. I worked up some loads for .308 on my single stage, and once I got it right, moved over to my 550. Well, 100 happy rounds later I noted that the rounds will not chamber. Checked in the guage (which I should have done earlier ), and found that I did not get the die low enough since the shell plate does depress slightly on the 550 and doesn't on the single stage. I now have that fixed, and 100 rounds to take apart..