Years ago I built a .50 BMG using plans from Maddigriffin, as Jim points out building the barrel requires very special equipment not found in your common machine shop. It’s not that big of a problem as you can get pre-chambered rifled barrel blanks from many manufactures (I used Walther precision in GA). This will also save you the cost of buying the chamber reamers (rough&finish) although you will need to buy a set of go/no-go chamber gauges to set head space (unless you have a precision grinder (.0001). For the rest of the rifle you will need a mill, lathe (must be able to thread), equipment for (proper) heat treating, TIG welder, measuring equipment and tools for assembly. If your rifle is to have a stock you will also need all of the wood working equipment as well stock duplicator, chisels, scrapers, rasps, sanders, etc. The same goes for finishing both the wood and the metal. Also needed is proper knowledge of how to use the above equipment (your not making bookends for the wife). If you haven’t figured out yet, it costs a lot more than buying one; however, I understand that’s not the point. Once you are done you will have a rifle that is not transferable (you can’t sell it) unless you also got your FFL manufactures license. As above good book to read over to get an idea of the amount of work we’re talking about is “Building a single-shot, Falling-block RIFLE ACTION” by Walter B. Mueller (Jim’s link is above). *** I just noticed your location, the most important thing your going to need is permission from your government (in writing). For the above project I contacted my local BATF office to make sure I wasn’t doing ANYTHING illegal, as the penalties are severe. I would imagine more so, in your case.