I have a .300 Weatherby Ultralight. It's really accurate, my best is 1 1/4" Somebody who could shoot could probably do better. I've noticed that after about 6 shots it starts to string up. At about the 10th shot it will be about 8 inches high at 100 yards. That's letting it cool somewhat, not 10 straight shots. It has a very slender barrel contour, stainless, fluted. I've never had a rifle do this before. Is it just because of the slender barrel? After it cools down it shoots right back where it was originally hitting. I use this rifle just for hunting, it's not a rifle I like to sit and shoot all day, but I am concerned if there might be something up with barrel. Thanks...