If I may suggest, check the below websites. The Americanlongrifles site dedicated to gun building. It's loaded with guys willing to help. The Toadhall website is Steve Bookout's. He is a retired builder now but used to have a barrel welding class once a year. He is one of the most experienced barrel welders I know. He authored a couple of small books on building a barrel rifling machine.
http://www.americanlongrifles.org/forum/
http://toadhallrifleshop.com/