I just clamped my butt pad in my mill vise and drilled a 3/8" hole just deep enough for a 5/16" threaded sleeve.
then drilled a smaller, deeper hole just big enough for the 5/16" allthread to go into and turn without binding.
Find a suitable handle. the round one is off of an old drill press I had. The other one I made.
Works like a charm.
