Richard, the O ring semi floats the barrel by reducing contact with the forend, ideally the barrel will only have contact with the forend at the barrel stud and the very rear portion of the forend. It works sometimes, or it can have no effect, but it's worth a try. I use an O ring that measures 9/16"OD x 3/8"ID x 3/32" thick on those barrels that it helps.