I have never had a rifle that would shoot boat tails and not shoot flat base bullets. My opinion is that to shoot boat tails well the barrel crown has to be absolutely perfect, the base of the bullet on a boat tail is in the turblent area of excaping gasses at the muzzel for a much longer time than a flat base bullet is, so is much more affected by any small irregularities in the crown. Could also be the way you hold your tounge when you shoot I guess. Larry