VAP explained it well. Remington approaches this a little differently than others. They place a high spot (pressure point) toward the end of the forend. This does much the same thing in that it causes the vibration that Vap mentioned to be the same every time. A pressure point will retain pressure regardless of the temp. of the barrel either cold with the first shot or hot after several shots. I have cured accuracy woes of several rifles just by loosening the forend screw and placing a piece of something like a matchbook cover between the barrel and stock at the end of the forend then tighten the screw again and your done. This works many times and is always the first thing I try if I am having accuracy problems. An old gunsmith showed me that little trick about 40 years ago when I had a 6mm Remington that just would not shoot. He said if that fixes the problem just put a little water seal on the carboard so it wont deteriorate from mosture.