Just a suggestion but you might try min-wax tung oil finish, it is not real tung oil but a type of polymer finish that will become very hard and tough after 2o or so days of curing. might give you a finish that you seem to be after. It is much tougher than true oil by far and has a warm look unlike lacquer. I have used this product to refinish the 31 very expensive 4 inch thick Koa wood dining tables in my wife's restaurant, Kilauea Lodge, and they have held up to their daily traffic very well for over 6 years now and still look good. If the restaurant owner was willing to trust me to use this finish on these expensive fine wood tables worth well into 6 figures it might just suit your fine shotgun needs too. most important thing is you must give it the needed time to harden correctly.
Aloha