Was out shooting this morning and was shooting one of my sportierized Swedish Mausers. This is a rifle I have a couple 100 rounds through with no problems. Was shooting a new mild load of 140gr Rem PSP's. 1st three shots went off with out a problem. However on shot 4 there felt like 2 stages of the firing pin going forward and a noticable delay of the round going off. Bolt opened okay, recoil felt normal, but the case was extremely dirty and there was carbon all over the rim area of the case and the bolt face is very dirty as well. Any thoughts out there as to what happened? Never had it happen before.