ok here it is. I am shooting a 308 rem700 kreiger barrel choate stock. the round is a 168 smk over 43.9 grains of varget, tull primer and winchester case. it leaves my 26 inch barrel at 2670. this gives me really good accuracy out to 600 but at my 850 target these rounds are keyholeing and my accuracy is gone. are these bullets going transonic and will more speed stablize them or should i go to 175 smk and what muzzle speed do i need to look for to keep them stable at that distance? I know the 175 have a better bc.