Mike Marlow wrote:
....
Anyway, he's at this point where he now has some amount of Tung Oil on the
walnut and some areas are showing a nice gloss, or sheen better than others.
Maybe because of uneven penetration/absorption of the Tung Oil, or maybe
because of the character of the wood. He'd like to even out the luster
across the entire piece. Also, I have to ask if he should be mixing up his
Tung Oil with a varnish and possibly some Turpentine and applying a couple
of coats that way in order to achieve more of a protective coat. This is a
grip for a bow and it will be subject to body oils, to weather, etc.
....

Probably the sheen difference is owing to a difference in both the wood
itself if it is glued up stock (as I presume it would be) and difference
in how thoroughly the sanding was prior to finishing. I would rub out
two or three more coats using 400 grit wet/dry sandpaper as the next
step to see how that goes...

As for long-term durability, the oil finishes will not stand up to water
well, but the good thing is they can be replenished easily...