Another way to skin that cat is with varnish. Sand between coats until grain fill is achieved, then keep going for a couple more coats. Use gloss spar varnish for its superior UV resistance. Rub out the final coat until it's dull looking, then wax the bejapers out of it to bring up a nice soft luster.
Intended use of the gun determines what kind of finish, IMO. Something that's going to spend a lot of time in the woods and inclement weather deserves a barrier finish. Just my opinion.
