Man with No Name- Mound-Protected Rifleman

  Just below the top he paused for a moment to catch his breath, then peered cautiously over. Some thirty yards to his left was the circular mound of rocks with the look of a manmade observation post. He caught a glimpse of movement and a flash of sunlight on a rifle barrel behind the rocks.
...

  Up on the mound, the rocks were moving, parting just far enough to let the muzzle of a rifle poke through. The hunter threw the barrel of his pistol across his left forearm, sighted and fired. The muzzle of the rifle vanished with a loud clatter.

- A Coffin Full of Dollars, chapter 24