It, extremely poor accuracy, can happen to a well used but not well cared for rifle. My dad had a Marlin 30/30 with the micro groove barrel. He was terrible at gun care, and one day that old rifle went to 'minute of washtub' accuracy. We kept putting up bigger and bigger targets, trying to get something on paper. Finally did, but groups (if you can call them that) were random and about 2 feet in diameter at 75 yards. Rebarreled.