I just got a kick out of this video. Forming tanks with explosions!
Hydroforming and even explosive welding (cladding) I’m familiar with, but I think explosive forming of a weldment is just something else. Not expanding the welds at such a different rate that they tear open. Pretty cool.
I’ve noticed that once you get past a certain point in the world of “big things” you start doing things like a6 year old boy would.
What if we just made a Minecraft looking tank and then EXPLODED inside it? It’d round it out AND test it at the same time!
“Dear Mythbusters…”
Inside every grown man, there’s a 12 year old boy. And inside every 12 year old boy, there’s also a 6 year old who still thinks that the word “boogers” is absolutely hysterical. 
I’d love to know how this got worked out first. It almost certainly involved a napkin and a bar. “I bet this will work!” “There is no possible way this will work. Wait. Unless you… hm…” “Hey, boss, can we try something insane?”
I just love the part where a car alarm goes off after the blast. Like is this the first time they’ve tried this here, or somebody ignored the no parking signs after driving past the ‘CAUTION: BLAST ZONE’ signs? 
So many times code has gotten much better after trying something that seems at first like a bad idea – especially ones that look at something that seems critical and ask “what if we didn’t…?”.
What sort of impact would explosive forming have on the work hardening of the material? Is this the sort of thing that might have some extra benefits in terms of making a really, really hard metal out of the deal?
It looks to me like the main thing the explosion does (it seems the tanks are filled with water but I don’t know) is turn it from a badly rendered Minecraft polygon tank to a round one - so it’s already sealed and welded this is just shaping it.