Linseed oil doesn't protect wood from water, ehh...whut?
I would use TruOil if wanting to get a "new gun" kind of finish. If it's an older gun, motor oil is all you need if you are looking to preserve the wood without really changing its character.
ANY, and all oils will protect your stock to the depth it has infiltrated. Some have polymers or a varnish that will also coat the wood as a part of the protection, TruOil is just one of them, anything labled as Tung Oil is high on my list of wood protectants. I've used TruOil on gunstocks before and Tung Oil on an unfinished set of swivel chairs and I would do it again or swap the purpose for both of them as they've performed so similarly.