It is possible to Zero a rifle scope with one shot. Use a material like newspaper or a large piece of cardboard behind the target to create a large area for the projectile to hit. Align the scope to the center of the target and fire one round. If you can see the impact point remove the adjustment caps from the scope and focus the scope back to the center of the target. Now looking through the scope gingerly adjust the radical in the scope to the impact point by using the scope's windage and elevation adjustments. You are now zeroed with one shot.