The Hornady O.A.L. Gauge is a precision tool designed to determine the maximum overall cartridge length (O.A.L.) from any firearm and produce handloads with precise bullet seating depth. It allows users to monitor throat erosion and check new or used firearms for freebore condition. The gauge uses the user's own bullets for utmost precision in measuring the initial distance a bullet travels.
Hornady recommends a free-travel of .020" to .040" between the bullet and rifling lands for hunting rounds.
No, you should not resize modified cases as this will ruin the case neck diameter.
Hornady requires a check or money order for $11.00 for each order of factory modification.