From the amount and color of the smoke, and the orange flash, I'd wager strongly that the explosive was old-fashioned black powder, the nitrate, sulfur, charcoal mixture you can buy in up to 50 lb kegs from any good reloading store.
You don't need a blasting cap to detonate the stuff, a spark will do, and it has a faster burn rate than normal smokeless pistol and rifle powders. It deteriorates fairly quickly, (Short self life), and it's highly hygroscopic.
I'm guessing a simple electrical timer wired to nichrome wire as an initiator.
“From the amount and color of the smoke, and the orange flash, I’d wager strongly that the explosive was old-fashioned black powder, the nitrate, sulfur, charcoal mixture you can buy in up to 50 lb kegs from any good reloading store.
“You don’t need a blasting cap to detonate the stuff, a spark will do, and it has a faster burn rate than normal smokeless pistol and rifle powders. It deteriorates fairly quickly, (Short self life), and it’s highly hygroscopic.
I’m guessing a simple electrical timer wired to nichrome wire as an initiator.”
And attached to every pound of BP is a long paper trail (with the buyers name on it). Which makes me wonder if it was something else.
The paper trail is required and one of the dealers in Houston lost his FFL because he was missing the paperwork on a small amount of BP.
I am sure they know what the explosive was by now and if it was BP every dealer in the area is being audited.
Although the bp lights off faster than modern powder it is nowhwere near as fast as modern powder. Much of burns as it is pushed out the end of the barrel.