If it was just one, how many reloads did you have out of that case. It sounds more like a neck tension if it was only one to me. Though I admit I do not crimp any .223 at all. Mine have worked just fine and dandy in several different AR rifles. Though almost all of mine are fired in my bolt action Savage.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.