I had the same problem with a new Stevens .308. Just the flyer part. Not only the 3rd shot but all subsequent shots. The gun has the sporting barrel and does heat up fast. The first 2 shots are one hole and after that they string. After running a couple hundred rounds it has improved quite a bit but if I slow way down it groups sub MOA. It is a great hunting rifle, 1 shot 1 kill. All shots in a 10 shot group would be a kill shot but I don't intend to shoot more than 1 at a time hunting. The gun does exactly what it is intended to do.
As for the primers pushing out, are you sure you are using proper (berdan, boxer) primer for the casings you reload?
"War is an ugly thing, but not the ugliest of things. The decayed and degraded state of moral and patriotic feeling, which thinks nothing is worth war, is worse. A man who has nothing which he cares more about than his own personal safety is a miserable creature, and has no chance of being free unless he is made free and kept so by the exertions of better men than himself" John Stuart Mill
Last edited by dteed4094; 10-19-2010 at 07:42 PM.