Hopefully MCMXI will chime in and can give more info on the history of the Hunter stocks and which ones are filled or not.
Every Hunter stock is supposed to be filled with ~8oz of rubber. This is done by the vendor in Syracuse that makes the stock, and using a machine that Kimber paid for that mixes part A and part B of the rubber compound. The grip cap is supposed to be ultrasonically welded onto the stock after the rubber is added. A plug in conjunction with a specific stock angle are used to aid in the filling process. Is it possible that some stocks left Syracuse without having fill added ... yep. Is it supposed to be that way .... nope.
