Spotting rifles were most commonly used with recoilless rifles as anti-tank artillery, from the 1950s to the 1970s. These weapons are used for direct fire with visibility to the target. As recoilless rifles have a relatively low muzzle velocity and thus a high trajectory, accurate ranging is important An optical sight can measure the bearing to a target, but not easily or accurately measure the range. Optical rangefinders were too large for lightweight portable artillery, and the later development of laser rangefinders would in turn make spotting rifles obsolete.