I have a 16" Stag, chrome lined, 1x9 twist, Nato & am shooting 55gr-62gr & 69gr bullets 250-300yds. By going to a custom (Krieger,White Oak) barrel,Wylde chamber,1x7 twist, & shooting 68, 75, & 77gr bullets what will the group differance REALLY be. Will I get a 60-70% tighter group, or will it only be a 10% tighter group? Assume a perfect environment...mounted in concrete shooting 250 yds. What is the most cost effective alternative?