That estimate for an implosion weapon is a little low by my reckoning, for it to be even remotely in that ballpark it&#x27;d require extensive reflection and other trickery. Without doing the math, I&#x27;d guesstimate a more realistic number to be about 1&#x2F;3rd to 1&#x2F;2 that neededfor a realistic implosion weapon.<p>But an implosion weapon is infinitely more complicated, even if I hand you all the material it just isn&#x27;t going to happen that someone would be able to build it in their garage. The concept is pretty simple, but there are a lot of little gotchas and also the machining and electrical tolerances are impossibly difficult without very specialized tools even if you had detailed plans. The design for the initiator in particular was notoriously a major problem during the Manhattan project and they really weren&#x27;t sure if any of the ideas they had would work.<p>Gun-assembled weapons are simpler but still pretty complicated. I&#x27;m not sure there would be much benefit to using only 10kg of U-235, which is <i>way</i> subcritical. You&#x27;d get a tiny bit of extra boom and some nasty isotopes from the fissions, but strapping some Co-60 to a bomb would probably be more effective. For comparison, Little Boy used around 64 kg, though that was more than the minimum needed.