Think I'd set it up in a 5 ton arbor press and push it out rather than beat it out. A hydraulic press like a Harbor Fright would work too but you have to fixture the gun under the press ram carefully. I'm opposed to beating them out. One slip and you screwed the pooch. One thing about using constant pressure is, you don't need a concave punch so long as you carefully apply the pressure and center the punch on the end of the pin.