Hello. I am considering building a rifle from scratch. I have an idea on how I am going to build most of the rifle but, I am unsure about a few things regarding the barrel. The calibre will be 5.56mm X 45. The length of it will be either 10 or 14 inches. Things I would like answered are: What diameter should the barrel be? What should I use to drill the barrel? Ie what type of drill bit? How can I rifle the barrel? If you think I need more info, please give it to me. I am wanting as much info as I ca get before I start the project. Sean.