There are a ton of reasons this could happen, as far as muzzle loaders go I consider myself a expert if there is any such thing but for years I fired over 30 lbs of powder in competition..... and have seen just about everything that can go wrong, double charge of powder,double loaded projectile, double loaded<<<<< this one is a barrel buster.... but the biggest thing for me is all the new synthetic powders, pellets, sabots and inline configurations it is all a recipe for failure, muzzle loaders loaded and used the way they were intended are pretty freeking safe we built them and double charged them for proofing the barrels never saw a failure with a patched round ball or a cupped mini ball, but have seen many with solid bullets and copper bullets over loaded... so the gun may have failed but i would be there was some human problem associated with it...