I have included the URL to Lilja barrels contour page.
This will give you the diameter information you wanted.
My last barrel was a Montana Rifleman barrel with a 9 1/2 twist and I am very satisfied.
You will want to use a 26 inch barrel for the size of case you are shooting, provided that you stay with 7mm Rem Mag or larger.
Lilja Precision Rifle Barrels - Barrel Contour Data