OP has described pretty much classic symptom of excess end play - between the bolt face and the chamber shoulder - upon firing, the case is driven forward within the chamber - primer ignites and neck and front case area expands tight to chamber wall - pressure pushes primer against bolt face - but not enough pressure to blow the case head back to the bolt face - leaving the primer "proud".
Could be undersized cases, could be excessive wear on rear of rifle's bolt lugs, crushed bolt lug seats, worn chamber - if the symptoms bother the OP, should probably get the headspace checked with proper ground steel headspace gauges.
If the rifle has more than maximum head space (FIELD gauge or a .010" shim between bolt face and GO gauge), then probably should not be used with factory ammo - but you should be able to re-size the fired brass appropriately, if reloading. SAAMI calls out maximum chamber at 1.6117" and minimum at 1.6017" - so, 0.010" difference between Min and Max - factory ammo should be in there, somewhere - bolt face to headspace datum along the case shoulder. A REALLY "rough" way for home guy to check - if three layers of tape on 4 or 5 cases allow the bolt to close - is VERY close to Maximum headspace, if not over it.
