Broke parts, jammed gun
My friend was shooting his 500 Smith & Wesson revolver (Buffalo Bore) and his gun tied up tight.
We shoot it around enough to open the cylinder and get it unloaded, but sometimes the action could cycle and sometimes it wouldn't.
Eventually, it went to a local gunsmith, S&W repair center, who opened it up and found part of the sear mechanism had broken off, jamming other parts from moving. He also declared that the firing pin spring had lost its temper and the firing pin itself needed to be replaced.
A pierced primer had allowed the pressure to blow back against the hammer and break the part, and the hot gasses had cooked the spring and firing pin.
Smith & Wesson made good on their warranty. He has cooled on his enthusiasm for Buffalo Bore.