Rods have a removable pilot and are made of steel.
This Range rod is tapered so that when inserted into a non-chambered barrel blank, a small section of the rod will protrude from the bore. The rod will be aligned with the center of the bore due to the pilot and the rod's taper (near the end of the rod opposite the pilot). The rod can then be used as an index point to assure that the blank is centered in a lathe prior to any machining operations.
If using a pre-chambered barrel, a PTG Indicator Rod will work better, since the taper in that rod is much closer to the pilot (the rod will center in the throat area of the chamber and still protrude from the barrel at the breech.
