Mark at the upper end of Hundred Springs reservoir. That is a .22cal Stevens Model 70 Visible Loader, which was my favorite gun. It was a pump action that is depicted in this VIDEO.  I used to take this gun hunting. It doesn't have a safety but instead you have to put the hammer on half cock (pumping the slide to feed a bullet in fully cocks the gun).  Unfortunately, no one told me about this and I would carry it with the hammer in the down position. One time we were out hunting and I was climbing over an obstacle and tripped and dropped the rifle.  The hammer hit on a rock and the gun fired going over my dad's head as he was ahead of me.