suggestion... take a few of your short cases, "by your measurement", an change the seating depth of your bullet so as it is into the lands of your rifling.. this will put some pressure agaist your bolt face... if they don't fire then... in theory.. you may have softend the necks to much in annealing, an the heads are pushing back into the case, or your firing pin has worn just enough to show up on the short cases.. or there is dirt you did not get out from in the bolt doesn't take much..take it apart., or you got some bad primers
2cents worth
2cents worth