I have been reading many posts and other references in preparation of making my first batch of black powder including accident reports. I have a 15 lb capacity rubber lined rock tumbler (Thumbler's Tumblers) and 200 brass 1/2" beads. If I am making standard black powder with this setup what is the likelihood and possible causes of unintended ignition? Would static be most likely culprit? Does the biggest risk occur when opening and dumping out BP and beads? Seems like using sparking milling media and milling more reactive mixtures other than BP are the most common causes of accidents. Is this so or have I missed something? I have a back yard but can only get about 50 ft away from house and neighbors. Digging a pit will not be well received by wife but do have some tires I could place around the tumbler. Going to try to convince a friend who has a farm to do it on his property by fear his wife will nix it. Going to try to join local pyro club so perhaps through them I can find a safer place to mill.