"To note on the cam pin wear on its lead in to its recess in the upper its normal as has been said.
But also keep in mind heavy or excessive extractor tension from the use CRANE o-rings and/or heavy extractor springs will cause the cam pin to bear even more(likely increasing wear) on the upper receivers cam pin track as the bolt tries to snap the extractor over the case rim and go into battery.
There can also be tolerance stack in the bolts extractor channel that could cause the longer extractor springs to coil stack.Have also seen enough tolerance stack to cause a CRANE o-ring to effectively seize the extractor.Have seen cases of the bolt bouncing off case head on in battery,and case rim damage(including excessive brass shavings fouling bolt face cartridge seat) from tolerance stack and/or excess extractor tension.There is a fine line there,too much extractor tension is just as bad and too little."
