Lengthening forcing cones dropped the point of impact on two drillings by six inches. Happened to one as a learning accident, and the other by design to correct patterning on a gun regulated to shoot high. I have not noticed such a change on any other configuration, and have done it to all autos and pumps...but I do it myself, so the price for the reamer just keeps getting cheaper. I don't plan to use fiber wads. Steve