Just a couple words of caution. Apple tree wood can be beautiful, but it can be really dense and hard; however that is a matter of working technique.
The biggest problem I have sen in trying to work with it is that the trunk has a lot of stresses in it (probably due to the way the tree grows and the repeated weight of the fruit out on the ends of the limbs) and it can twist like a snake once you start removing wood form a slab. Now bear in mind that this is based on a regularly pruned and maintained apple tree. If you found an old feral one out is an abandoned farm site that had grown taller and straighter, maybe it might make a difference
Some years ago I tried making a simple set of S&W pistol grips out of a well-seasoned chunk salvaged from an old treasured family heirloom Cortland that we lost in a storm. I profiled and book-paged the chunk and routed out the interior for the frame and innards. (It was way to hard to hand carve.) 2 days later the thing had warped to where the two routed out pieces would only touch in a couple spots. I tried working with the wood on a couple other projects for the family as well but in each case the stress relief warping defeated me; leaving me very disappointed and frustrated
IF I were to try to make a LR stock of apple, assuming I could find a chunk long enough, I'd rout the barrel first thing and clamp the barrel in place immediately and try never to take it out any more than absolutely necessary. Even with that I'd worry about the wrist and lock inletting areas so I'd be offering apple pies to the stockmaking gods on a regular basis to keep that wood from warping like a snake uncoiling in very slow motion.
I would love to hear of some techniques for working with apple wood successfully. I seem to recall of it being used by new england gunbuilders, and I still have access to some very big old ones on family property