I have a Savage 12 Low Profile Single Shop in 204 that doesn't shoot as good as I would like. Thus, this gives me a great excuse to build another caliber as I have a Ruger 77 in 204 that shoots great. Am thinking of ordering the Shilen barrel in the 26" heavy sporter chambered in the 22 BR. Shilen has 2 neck sizes listed, a .244 and a .248. This is something I have never dealt with before so what do I order and what is the reason for the 2 different sizes. Thanks