A method of using an apparatus that improves aiming accuracy with manually operated firearm provides a means to support the front part of the firearm's barrel and moving the barrel in parallel with the movements of the firearm's butt. Small rotations of the firearm's muzzle are measured by high resolution angular position sensors and rectified by moving the muzzle mount of the apparatus in horizontal and vertical directions which result in rotation opposite to the measured deviation from correct aiming direction, thus preserving the orientation of the manually operated rifle parallel to desired aiming direction.