^^thats probably how it was reported to the police, so the guy was just referencing but he didn't really know.
@Killjoy: I agree it can be done safely, but hitting blasting caps with a hammer isn't even following basic safety principles.
Well thats kind of a given now isn't it haha. it was lucky the hammer didn't get blown off the handle and into someone, I'm seen some weird stuff happen with explosives go off near things.
come on, why would you make a pipe bomb (and I haven't done this or made any pipe bomb) with such an unstable or ignitable compound that it blows up when you are screwing the cap on!??!
One of the main problems is that people get the explosive compound in/on the threads and either forget or fail to properly wipe it off the threads, so screwing on the cap can create enough pressure and/or fiction to detonate the mixture. Thats why its always best to clean the threads extremely well, and if using powder as a filler, dampen the threads with rubbing alcohol to temporally stabilize any powder left and screw the cap on very slowly, which "stubs" obviously didn't do.
Of course people tend to use powder as a filler, which is very stupid as it can shift once closed if not properly packed and accidentally self ignite if it is unstable enough (such as flash powder), which is probably what happened to the genius in the bag.
Explosives are fun, but theres no room for error and rarely do you get a second chance. I've had a friend burn himself with acid trying to make nitrocellulose (not necessarily an explosive), and drop a bowl of flash powder which caused it to ignite, badly burning him. And I've been hit with shrapnel and been pretty burned from accidental ignition. Its just better to leave it alone unless your with someone who knows what they're doing and can teach you, and its best not to take the self taught route (like I did)