My .22 Mrod is changing POI despite fantastic accuracy using 18.1 JSB. At 35 yards it will deliver match head accuracy..dead on.. and then suddenly with the next shot move about 1/2 inch right. Always to right of my standard sight in. If I stop at that point and refill it will move back to left again for a number of shots. It must be related to the fill in some way, but is there a way to solve the problem? Would glass bedding the rear most portion of the tube and free floating the forward portion tend to resolve these issues?