Some years ago on a hunting trip we hunted in the rain all day. One of the fellows in camp shot a nice buck very close to him. In camp he passed around the empty case and it looked very strange. Nothing like the other two empties from previous days. The case looked as though it was ridged lengthwise, almost duplicating the look of the rifling in the barrel. He said he had the rifle leaning muzzle-up in the stand for hours in the rain. We all figured the rain had something to do with it but couldn't figure out the ridges. Anyone hear of such a thing or have any guesses as to why?