I want to build a 270 whatever is fast with a140 grain 400 + bc. at 3300 fps. Case is to be determined and is not a concern at this time! What concerns me is The "barrel" as to number of grooves,twist, shape of land grooves ie. 5r? And anything I may have forgotten about for ii! It's my first truly custom and don't want to forget or leave anything to chance! Any and all suggestions are encouraged and appreciated. Thank you Tribb