PCC piercing primers

[jrb06]

So has anyone had problems with their PCC 9mm hitting the primers very hard and sometimes even piercing them? This is not a overpressure problem as the loads have been chrono and are 134-136 PF. Have tried factory loads and reloads and all of them show the primer being hammered very hard. What is also odd is that it is CCI SP primers that are being pierced more than the WIN SP primers.

New Frontier Armory lower, their  heavy bolt group, their 16" barrel and standard upper receiver CMMG LPK.

First used standard buffer and spring primer problem. 

Then changed out to heavy 6.5 oz longer buffer. Bottoms out rearward 1/8 - 1/4 past bolt release. No change still occasional pierced primmer but very deep hard hit primers.

Reduced hammer spring tension for testing purpose. Appears to lessen the heavy hit but still more than what is acceptable and still found a pierced CCI primer out of 50 rounds.

So is it a case of the hammer spring to strong for SP primers or as someone else stated in a different thread the hammer is not bottoming out against the back of the bolt. I need to check that yet but wanted to see if anyone else has seen this.