The solvents or vehicle carry the oil into the wood. Oils such as linseed ( boiled ) and Tung are formulated with drier solvents that promote penetration. New wood if your referring to previously finished wood will of course absorb less finish as you can never remove all of a penetrated finish from the wood at the cellular level. Virgin stock is a blank slate and will always accept more finish. 

Another major factor is the inherent oil content of the wood species even fresh varies. Many species contain lots of natural oils especially tropicals like rosewoods, teaks etc. and even domestic like hard or yellow pines. Some cuts of walnut, the primary source for gunstocks, have more oils than others so nothing is black and white

Rick

Good luck. The stuff continues to shrink in the pores even after it's dried and cured - at least the times I tried it, so have given up on it. Perhaps the formula's been changed, I don't know.

I was given this today, anybody have any experience with Watco Marine Finish?   

(You need to Login or Register to view media files and links)
(You need to Login or Register to view media files and links)

Never used Watco's oils on yachts and honestly never knew any other professionals who did. From what I know Watco formulates a proprietary varnish/oil and I'm pretty sure all of their product line is just that with a few additives and some pigments. Years ago they sold lots of boat owners on their Watco Teak Oil for decks and trim but it didn't last long, hardly used on decks anymore. 

As a varnish/oil with several solvents or vehicles it penetrates very well but it's very low viscosity so won't fill and build. It produces an attractive color and is still used in the furniture circles. It used to have some serious drying oils so it's imperative to seal rags or they will flame up something fierce. My opinion is this product is well suited to gun stocks with several coats or pure oil or spar varnish. I know nothing at all about their filler product, never even seen it. 

Rick

I am very happy with boiled linseed oil.
Many years ago now I took out  a book from the library regarding making knives by either a Swedish or Norwegian guy   
or somewhere else in scandinavia who said that boiled linseed oil changed its composition over time in the wood. 
Looks like all knife handles are made of Birch there and some really curly Birch look fantastic.