What hand tools could I use to make a cheap prototype to see if something is viable?

I'm want to see if I can build a vz 61 reciever and see how difficult it is to make. I would like to afterwards get proper machines to make them but I just dont have a lot of money to spend on a prototype and machines. And I'd rather have nice machines and a basic prototype.

You'll certainly see how difficult it is to make something out of steel by hand, but what would be the point of that? If you want to make a prototype and don't have the equipment, take the project to someone who does, and make it worth their while to produce it for you. They can tell you how hard it was to do for them, which is a lot more relevant.

Hand tools? Really? It's POSSIBLE to build that receiver using nothing more than a hacksaw, a pocketful of files, and some sort of drill.

It's difficult. It's much moredifficult with machines, unless you're well acquainted with those machines and with machining practice in general. You can't just expect to throw a machine at a project; you have to learn your skills.