I have seen people use old blue jean pant legs, filled with kitty litter. Sew the ends closed. Light weight, cheap, and very effective. If you can align several by stacking on top of each other (front and back) so the crosshair lines up on the target without having to hold it in place, you should be good. You shouldn't have to fight it to get the crosshair onto the target. Any outward force you have to apply to the rifle will affect your group, other than just holding it firmly to control the rifle when it recoils. The lead sled will definitely cause damage to scope, stock, and other components if you have it weighted down heavily to prevent it from free recoiling. Especially if you shoot it numerous times. Without any weight on it, and allowing it to move back upon firing, it should be safe for a couple of shots. I use sandbags, and never a lead sled.