8-b, I have had good luck on stuck bullets with a brass rod. Like wood, won't hurt the rifling. Did you soak in penetrating oil before the oak attack? A 3/8" rod should work - - - just in case you don't have a 13/32" rod laying about. Also, a 13/32" drill with a 1/4" turned shank soldered into a 3/8" rod (steel or brass) and turned slow with lottsa lube (say, with a hand brace) should also take the offending material out.