The only times I can think of that you should have trouble with neck sizing ammunition as opposed to full sizing is if the magazine won't handle the expanded case, or if the chamber isn't exactly round. If the chamber is a bit off, then you can only re-insert a neck sized cartridge in the same position as it was when it was fired.
Oh, the third time you might have problems with neck sized cases is if you try to fire them in another rifle. Cost me $25 to learn that and to get the gunsmith to unstick the bolt on that rifle.
