Were these factory rounds or reloads? If reloads, they may need a small base sizing die.
auk1124 asked some important questions. Since you have a new barrel, everything fits extremely tight. You had some carbon around the neck of the round and the round got stuck going in. This happens with new barrels, especially if you are shooting steel cased ammo or ammo that uses dirty powder. All you need to do is clean the barrel and barrel extention. I suggest a can of spray carburetor cleaner and a .223 bore snake. You can use a cleaning rod and brushes as well. I'm a bit lazy so I choose the spray carb cleaner and bore snake.
kwg
