I got my Savage pre-fit barrel through Jim @ Northland Shooter's Supply. Check him out at
http://savageshooters.com/SavageForum/.
It is a Shilen and they call it a "30/221." It has a 1 in 8 twist. They will make it however you want, and charge $75 for threading. If you buy one through Jim it will be cheaper than the prices listed on the Shilen website.