Need to redo my eagle arms action master 20" and want benchrest type groups for hunting p-dogs at up to 500 yrds and target shooting. Ive decided to go 1-8 vs. org 1-9 twist but whos barrel should i go with for this ? I dont realy want to spend 4-$500 for a krieger! Or do i have to go with an all new upper to get this type of accuracy? And im thinking of A.I.ing it would this be a good idea or will groups suffer?