Custom barrel and chamber. Loaded with 4831 to drive 140's at 2800fps. Case stretching is often blamed on case design when it is really due to some other factor. My P14 in 303 does not stretch cases at all. The Lee Enfields do. I had one 700 in the shop which stretched cases badly (it was a 6mm Remington which had been re-barreled by Shilen). It turned out the problem was a bolt face which was not square. After truing up the bolt face and setting the barrel back to correct the resultant headspace, the problem was gone and cases no longer stretched.
Another common cause is a chamber which is a little on the large side. The shooter partial sizes the cases and, as the die squeezes the body slightly, the shoulder bulges forward. A couple of firings and sizings like this and the case goes in tight. Regards, Bill.;
