Real Home made guns? Answered

Hi there, i'm new in this site, but is there instructions here on making lethal homemade guns? Not just bbs or knex, I mean ones that are really lethal. or even beter, is there someone here that knows how to make lethal automatic guns? I wached mythbusters about the paper cross bow and discovered some inmates in the past made guns from plumbing materials. Is there anyone here that knows how to do somthing like that? Waht about home made ammo?