We had a Home burn down in 1999, I had allot of ammo and reloading stuff in the basement. Some of the ammo burst (some still had the slug in the case mouth). I had cans of H441, IMR4350,Unique shotgun powder,and others. All the powder either popped the lids or melted.And none of it exploded,it burned like a sparkler. The 4 lbs of black powder was a different story, It took out an 4'X8' hole in the wall between the reloading room and the computer room. The fire started at the junction of the electrical meter on the outside of the house and went into the attic and basement in about 10 minuets.