A simple gun rest when you have nothing is is a simple cardboard box. You cut V's in it and rest the rifle in the V's. Take any kind of weight and place that in the box to help hold everything together and solid to the bench. We used to use cardboard boxes all the time in deer blinds when we hunted long distance field for shooting. We alwasy built a short bench under the shooting window, and the box would fit right on that and hold the rifle up off the ground when nothing was happening. After your done, throw the box in the burn barrel and get a new one the next time you go shopping. Unless you grow attached to the box of course. Good luck at the range today.