Cut a piece of ¾-inch PVC pipe to a length of 18-inches with a miter saw. A miter saw ensures the end is flush.
Measure the depth of the slots on the barrel nut with a precision ruler. Transfer that measurement to the end of the PVC pipe. Measure the same distance from the end of the pipe, then wrap a piece of painter’s tape around the pipe at that depth.
Place the end of the PVC pipe against the end of the barrel nut, then place a piece of tape on the end of the PVC pipe to denote each slot on the barrel nut. The tape must match the width of the slot.
Grind away the un-taped areas between the end of the PVC pipe and the painter’s tape that goes around the pipe with a rotary tool. When finished, you will have a reverse image of the barrel nut’s end.
Coat the other end of the PVC pipe with epoxy. Butt the open end of a ¾-inch socket against the end of the PVC pipe. Give it two hours to dry.