have the 223 wylde 18" stainless 1:7 twist. Tried 5.56 and 223 in hornady, federal,winchester. bthp, fmj, 55 grain to 75 gr. i can not get this thing to group at 8o yds. bought 3" dia is the best i can do. i not new by any means to mounting scopes, that all seems fine. had the scope on other rifles with no problems. barrel seems tight. Contacted the good people at D.B. and they said they would send me a new barrel. Hope that helps, i really like the rifle other than the present problem im having.... any other suggestions.