BerdanSS - I asked my machine shop teacher. He didn't know any maker of 50 caliber 1:22 or 1:24 twist barrels. My classmate did (he's also NMLRA). He suggested Green Mountain. Here's the biggest I found. It will make a medium weight barrel.
I also checked Colerain and didn't find anything. Doesn't look like we can get a 2" thick barrel.
Today I learned how to cut on the fly. That can be used to cut the flats on the milling machine (instead of using a horizontal mill).