This may not be your issue but Ill pass it along. I had similar issue with a new 223 barrel that would close but light primer strikes (cartridges were slightly too long). Found out through Mike Bellm Articles that the cartridge needs to be .001 below the barrel to allow the barrel to fully close for the locking lugs to engage far enough to rotate the part that unlocks the hammer block and allows it to drop when the hammer is cocked. It appeared to me the hammer was striking the firing pin, but when viewed from the side the hammer was hitting the top edge of the hammer block with the impact sending the firing pin forward and tapping the primer.
