

This is actually something that a turing machine is suitable for.
Get youself something to remember what state you’re in, write the rules on a sheet of paper and use a stack of paper as the tape, with each piece of paper being one cell.
Turing’s idea was to build a mathematical model that mirrored how humans go about large, complex tasks.
Honestly, all of these super basic mathematical models for calculation are fairly well suited to being “run” by hand.
Random-access-machines can be done similarly to turing machines. Write the program down, keep the program counter on one piece of paper, and have a (numbered) stack of paper as memory.
And lambda-calculus is probably the easiest. Just write out the expression, and then write out each reduction step. This is what functional programming languages build on, and with the additional effort of checking types, you could probabl evaluate something like Haskell by hand pretty well.
All of those are turing complete (if you ignore infinite memory).
EDIT: spelling




I’m not sure if that’s true. I don’t have any experience with it myself, but lead is notoriously easy to cast at home, because of its low melting point.
So it seems to me, all it takes to make some (shitty) ammo is some lead, a mould (which you can make from clay) and an explosive.
For a proper modern gun, that last piece is probably pretty difficult, and you would need to make casings somehow too (I’m not sure how difficult that would be). But if you were using some form of (possibly homemade) flintlock or similar, the gunpowder from fireworks should be enough.
I think regulating both guns and ammo is the way to go.