As an add to Flag's post, make sure you are using a TRUE neck sizing die and not just an adjusted FL sizing die to do the neck. That way you aren't bumping the shoulder or sizing any more of the case. Personally, when I fire form, I use the cream of wheat method to fire form my cases. But that can be a little time consuming to find the right recipe of pistol powder load for proper sizing and shoulder forming. You should also learn how to anneal your case necks to prevent cracking/splitting and increase longevity of the case.