I've done a few and never had one blow, but perhaps I was lucky. I used a universal decapping die, since there's lots of clearance around the case and won't confine the explosion like a sizer will. The primer will exit the press at high velocity, so figure out where it will go and don't stand there. IIRC, Jim Bullock noted in Precision Shooting Magazine that he chronoed primers at 700 fps. He heated primed cases with a torch until they blew. As Mal said, wear face & body protection.