had a newbie to reloading do this once, so i dismantled the rounds that did not fire.
WOW:...............................................no main powder charge had been placed in the case, primer was fine.
if its not that you have the solution/advice above to sort it.
good luck
bob.
Was there visible signs the primer had gone off bob as per Muir's post? or did the round look intact apart from the firing pin mark?
Regards,
Gixer