I have had the opportunity to play with a Jewel/Foster setup. The first thing that I did was make sure that the rear adjustment and spring tension surfaces were centered on the spheroid contact ring on that is mounted on the scope tube, and hidden from view, unless the top of the rear ring is removed. Once I had the front to rear ring spacing, I mounted the assembly on my Viper action, and sighted in. There were no false moves. After bore sighting, I fired a shot, and then dialed the cross hair intersection over onto it. The second bullet hole took out half of the first one, and I did not see any subsequent shift. Some time later, I changed barrels, repeating the process, with the same result. I really liked not having clicks. The rifle is used for shooting groups. Once it is sighted in for a particular yardage, barrel, or load, I leave it alone.