I have a Rem short action rifle that needs re-barreled. Thinking of going to a 6mm Rem. or the 243 It will be a deer and hog rifle used out to 600yds. What length bbl, and contour, #3 or #4. What twist? What about a Brux bbl? I found one in stock, 8 twist SS, #4contour I have read that the 6mm...