TMR,
I would have to agree with Catshooter on this one. The problem with most modern center fire rifles is that they use a firing pin that is to **** large to begin with. Winchesters are terrible for this.
For a modern high pressure cartridge, a firing pin diameter of 55 to 60 thou is plenty large. Unfortunatly, most modern firing pins are more like 70 to 75 thou in diameter.
The larger the diameter of the firing pin, the more pressure is pushed back against the inside of the primer cup.
The larger the diameter of the firing pin hole, the easier it is for this high pressure to force the primer cup material back into the firing pin hole. Its a simple PSI over increased area issue.
If you have X PSI over a small area, the material supporting that pressure is more able to resist being forced back into that unsupported hole.
The larger diameter the unsupported area is, the more difficult it is for the primer pocket to resist this set back and you get primer cup flow into the firing pin hole.
This will happen in even very mild(for modern rifle) pressures. ANything much over 40,000 psi will do this.
If you are not having any problems with the function of the rifle I would not worry TO much about it.
Watch it as you develope your upper end loads and make sure you do not get near the point of piercing the primer. Also, if the receiver has been properly accurized you will not have much problem with this but if it has not and the firing pin is not hitting center on the primer, when you open the bolt, often times this little nipple on the primer will be sheared off into the firing pin hole which can cause several problems ranging from a firing pin wedging solid in the bolt and locking the rifle up to causing the primer to pierce on the next shot with the chips of primer material between the firing pin and the new primer.
Simply put, the problem is to large of a firing pin and firing pin hole.
If the problem causes real problems as the ones mentioned above, you can have the firing pin hole drilled out, and fit a threaded plug into the bolt face and then redrill the bolt face with a properly sized firing pin hole and refinish the bolt face. this is often not needed and the problem is seldom more then an annoyance but if it does cause problems it can be corrected. Also, the firing pin needs to be reduced to fit this smaller diameter bushing.
When you get your Nesika you will see what a properly sized firing pin will look like!!! /ubbthreads/images/graemlins/grin.gif
Good Shooting!!
Kirby Allen(50)