Could make a big boom if mishandled just right. It would have to be in a container that would pressurize the burn. Most gunpowder is sold in containers designed to allow it to burn rather than explode. It is classified as a “propellant” rather than an explosive.
I do not know exactly how it was contained. But it was likely about as dangerous as 10 five gallon cans of gasoline.
Right, of course.
I'd say less dangerous than that 300# of gasoline. The gasoline can create a potentially explosive mixture with air, gunpowder can't do that.
Actually a 10 gallon can of gas can make a VERY nasty air/fuel bomb if mishandled just right. But you are correct, not much threat from the gunpowder.
Rifle powder is not even close to being as dangerous as gasoline. You can dribble some H4831 into an ashtray and put a cigarette out in it. The slower burning versions of smokeless are hard to even light in open air. Gasoline is much worse, as are most aerosol hair sprays. It will burn, but not near as flammable as many household items.