I have a new rem.750 308 cal. I put a 6 in rail on it which fits perfectly I mounted a new weaver super slam on it 1in rings. With the hight adjusted all the way I cannot get it on a 18in target at 40 yrds. Just hits dirt. Then put a vortex viper pst on 30mm rings with the same results. The rail is not tapered. Need help before I call Rem.