I was always wondering,what would happen if you used regular firecrackers that are available to everyone and used about 30 or more middle or strong ones and combined them in one giant firecracker,would it be like a really small ,bomb, able to give some sort of a high pressure that would imitate a small grenade? (with the exception of shrapnels of course) For example would it be able to tear through thin wood,break a glass,etc? My little cousin played with just one middle strength one today and it cleared snow some 4,5 inches around it and f. up my ears,so I can’t imagine what 30 or 50 big ones combined would do… Also does anyone know how strong flashpowder is compared to regular tnt? Then it would be easy to calculate how much damage it would make.
Are you asking about sticking the firecrackers together or taking the powder out of each one and combining it?
http://www.fireworkssupermarket.com/Product/Firecrackers/Boom_Sticks This is something my dad used to use all the time when I was a kid. It has many firecrackers in it, and it just keeps on crackling for a while.
The pressure cooker bombs used in the Boston Marathon were fueled with powder from fireworks. You’re probably violating various state and federal laws if you start playing with these.
Back in my youth, when fireworks weren’t as restricted as they are now, we played with every conceivable mixture of firecrackers.
If you take, say, 50 firecrackers, bundle them together and tie them with a string, then light the one in the middle, what probably will happen is that the ones in the middle will go off, but the ones further out will more likely fizzle.
There’s a design involved in making fireworks go boom. If you don’t pack the powder and the fuse correctly, it may just burn, rather than explode.
Firecrackers don’t go off with enough force to detonate adjacent firecrackers, so there’s no chain reaction explosion. Also, the fuses in them are not particularly exact, so even if you duct-tape a bunch of them into a bundle and light all their fuses at once, they’ll all go off at about the same time, but no particularly additive effect, except maybe a bigger cloud of smoke.
nm - double ninja’d.
The bundle would begin coming apart when the first one went off, as has been stated, the fuses aren’t the same length.
Some would be burning and go off as they were blown away from the bundle, though. It would be cool. 
If your older cousins unroll enough to fill a small prescription bottle, it makes for a very impressive explosion. At least, it impressed me when I was about 10 years old, 40 years ago.
Same here. They blew up a traffic sign at 19th and Harrison. 