Primer extrusion question????????

[billy_56081]

 I started to notice primer extrusion in some ammo I was firing. The load was a load that was used before in the same brass as before. The only difference in the second round of loading this brass was that the primer pockets were trued up and the flash hole was deburred. I'm wondering if this may be a sign of excessive pressure or might it be caused by the flash hole being enlarged while deburring?

[Grumulkin]

Perhaps you mean primer protrusion (i.e., primer sitting up above the level of the case head after firing).  This is usually caused by low pressure and not by high pressure.  With high pressure, the primer will be flattened at the level of the case head.  With more severe high pressure you start getting primer leaks or pierced primers and no protrusion.  In addition, enlarging the flash hole during deburring won't happen in the first place and if it did would make it LESS likely for the primer to protrude.  In fact, when shooting rubber primer powered bullets (very low pressure) one must enlarge the flash holes with a drill to keep the primers from protruding.

If you really mean extrusion (i.e., metal from the primer being pushed into the space around the firing pin hole), that is caused by high pressure.  Most refer to this as cupping.  It could be caused by an enlarged flash hole but I have never had this problem when uniforming primer pockets.

[steve4102]

  What are you loading for and what is the bullet and charge weight?  As Grumulkin stated,  backed out primers is usually a sign of LOW pressure not high.

[Questor]

I may be interpreting the question wrong, but are you saying that the primers are loosely fitting in the case? If so, the cases are worn out and need to be replaced.

[billy_56081]

The primer is flowing back into the flash hole. A classic sign of high pressure. The odd thing is, is that when loaded the first time with the exact same recipe, there was no flowing into the flash hole. This only appeared on the once fired, trimmed brass that has had the flash hole deburred and the primer pocket trued up. That is why I am so confused about this as in the first firing of the brass I had no pressure signs. only after deburring the flash hole.

[John Traveler]

Another factor may be at work here causing your high pressures.

Did you trim the cases back to minimum length after that one firing?  Some cartridge/rifle chamber combinations can make the brass "grow" excessively after only one firing.  An overlength case will certainly bump up firing pressures on the next reload.

[billy_56081]

Yeah the brass was trimmed to minimum length. This is just a mystery to me. This is the same brass. The same primers. And the same powder charge of the same bottle of powder. The only difference is the brass was resized, trimmed, the flash hole deburred and the primer pocket trued. Could I be getting better ignition from the deburring of the primer pocket and truing up the primer pocket?

[steve4102]

The primer is flowing back into the flash hole. A classic sign of high pressure.

  How can you tell if the primer is "flowing back into the flash hole"? 

[beemanbeme]

I'm gonna make a wag (wild a$$ed guess) that he has been over zealous in prepping his primer pockets and also his firing pin hole in the bolt is a bit over sized.  Primer flow around the pin with no other signs usually means only that.  And it is not unusual in modern rifles.  The reason it didn't happen with the first firing was the pocket was much snugger.