An oil finish is the traditional way to go, it is time consuming but pleasing to the eye if done correctly.
You can seal the grain using varnish, allowed to soak deeply into the wood (thin the varnish to a watery consistency) once dry sand back and then commence applying oil finish, a little but often, to do it properly normally takes about 4-6 weeks.
I actually have the formula for Purdey's famous slacum oil finish.
Similar oil kits can be bought from gunshops, Michael Smart's 'Trade Secrets' is one I can recommend, CCL is another, good but not quite as good in my opinion as Trade Secrets.
Napier London Gun Finish is a modern quick finish, very good but contains polymers (varnish) to quicken drying time.
If you are really keen you can go on www,doublegunshop.com look up 'Salopian's Slacum finish', it is all there telling you how to do it and make one of my concoctions.
Any problems send me a message.
Take your time, it will be well worth it, especially if your wood has any figure.