Too slow a powder will do this, also poor primer and/or poor crimp. Was this in daylight?
Find out his recipe(powder/cal/proj.weight etc) and we can help!
But maybe your buddy likes the effect
------------------
If we shooting sportspersons don't hang together... we will all hang separately !
Never knock another's different shooting interest or discipline...REMEMBER we are all but leaves on the same tree of freedom.