Tell that to be BP factories back in the 1800's who blew themselves up on a not to infrequent basis. If I am not mistaken, not all of the BP-making process is done wet. Also, if you aren't very sophisticated, you will end up with what is known as "green powder", which is BP, but not a commercial grade. Suitable for pyrotechnics, but probably not guns. Commercial grade is not that easy to make from what I understand. Involves more than just "mixing" the 3 ingredients together.