I am considering building my own rifle, either a 7mm or 30 caliber. What would be the best barrel twists for each of these calibers? I wantthe rifle to be good for everything fromantelope to moose. I would shoot a 140-160 grain bullet in the 7mm and a 180 in the 30 caliber.My choices for the 7mm are 8, 9 1/2, 10 and 12. 30 caliber are 8, 10 and 12.