It can happen, even to careful reloaders... I knew a guy who accidentally grabbed a can of Winchester 231 instead of the Winchester 296 he wanted for a .44Mag load!
As I recall, about 7 gr of 231 is a very nice, light load with a 240gr LSWC bullet. About 29gr of 296 is a very heavy load wih the same bullet. This guy put 29gr of 231 behind that bullet! It blew the cylinder apart!
Mark