US Patent 7121032 Hydraulastic recoil pad for a shoulder firearm

A recoil pad for a shoulder firearm includes at least one piston member that is caused to move axially from an initial axial position to a second axial position upon application of the recoil force from the firearm. The axial movement of the piston member causes fluid movement within a column relative to a variable or fixed orifice area wherein the fluid movement causes resistance that absorbs the energy. A mechanical and/or hydraulic and/or elastomeric feature returns the piston to the initial axial position upon cessation of the applied recoiling force.