Just to clarify, my huntsman came as a .50cal ML/.243 Win combo from NEF. no one wanted it ( appearently ) as it sat for a few years at my local gun shop. i paid $295 for the set. its marked NU, as i understand it, that means the date of manufacture was 2004. so your though about NEF stopping use of plastic sights could be accurate. no matter if they would exchange them or not, i fixed the issue myself, but i would have infact kept the sights had they been metal
i'll describe it best i can, there are three screw holes, tapped into the barrel, they are at the breech plug end of the barrel. the first one is about 1 inch from the end of the barrel, and it goes clean thru the barrel and you could thread a screw into it and hit the breech plug threads. from what i understand, thats how it came from the factory. using the NEF original factory screws that are used for the scope rail, is not an issue, its short enough not to cause problems, after market screws may be an issue. im sure its not an issue as the pressure will be on the other side of the breech plug, as witnessed by the other two screw holes are not thru holes, they are where the pressures would affect them when firing.
i hope i explained it well enough. maybe others with huntsman's will comment and compare mine to thier findings
glenn