Sniper fill is just more of a dense fill in the action area. Its solid fiberglass with our epoxy instead of sporter fill which is just less dense fiberglass and fiberglass micro bubbles. Also, in sniper fill we fill the butt of the stocks with real light weight fiberglass and in sporter fill we fill the butt with a dense foam. The forearms are filled the same way. Really sniper fill is only needed for heavy recoiling rifles like .338 RUM or if your wanting to torque your screws down to 65" lbs. To be honest, some guys just get it because they like the name "sniper fill".