To stoolshooters point -brass can harden over time. At manufacture the case necks are annealed at the factory to prevent gas leaks and to hold the bullet over time.Many in the competition arena are aware the problem with splitting case necks. Norma, on their website, states that this annealing should hold the bullet tight in the case " for at least 10 years". Next time you shoot some vintage brass, look closer at the fired case necks.... there is a good chance that you will find upon close inspection that the necks have split. Research conducted many years ago at the Frankfort Arsenal concluded that oxides of nitrogen are formed during the aging of smokeless powder which may cause season cracking of the brass.stoolshooter said:What I have found is that over time, bullets tighten up in case necks. Try pulling bullets that were loaded year or more ago, you will find out. Overly tight bullets increase pressure and will change your POI.