I think I found the problem with the Remington 700 (264 WM). Apparently Remington in their infinite wisdom puts a pressure pad about 2" back of the forend tip. This places upward pressure on the barrel. I believe this could be causing the wood stock to change as the barrel heats up. As you can see in the pic, I sanded off the pad and can now pass a dollar bill (or two) completely under the barrel all the way to the recoil lug.  I will be heading to the range tomorrow if the weather holds to test my theory.