The other day I had fired maybe 40 rounds thru my no 4 Mk1 when it stopped firing. The ammo, a cast bullet gallery load, was all loaded the same, primers and all, in the same session.
Upon pulling the trigger the firing pin would fall, seemingly normally, but the primer was not marked. The firing pin was inspected but was fine. Upon testing, there were some misfires, two rounds fired then back to misfiring. I never had a misfire prior to this.
Any suggestions as to what might cause this?