you can use a solvent to help pull the old stain, if stained, out, and sand it smooth and clean with progressively finer papers. Once done, you can choose to stain it with whatever shade you please. once you finished staining it, I use birchwood casey true oil to set the stock. 6 to 8 coats adds a nice clearcoat sheen.
God never made a more beautiful scene than the sunrise I saw this morning from my treestand
I also sand off the old finish starting with 100 grit...Then 200 grit and finally with 400 grit always sanding "with" the grain of the wood. You should keep the buttplate and pistol grip cap (if so equipped) in place during sanding so you don't remove too much wood at the joint with the metal, plastic or rubber. Now the stock should be nice and smooth but it is not ready for finishing yet.
Take a damp rag and wipe the whole stock down to raise the grain. After it dries you will notice that it now feels fuzzy. go over it again with the 400 grit. then wipe it down with the damp rag again and sand again. Do this until the stock stays smooth after wiping with the damp rag. Then go over the whole thing with a tack cloth to remove all of the sanding dust.
Now you can stain it with the stain of your choice. After drying, I finish it with Formby's Tung oil. I normally apply 6 coats or so and go over the stock very lightly with 0000 steel wool and a tack cloth between coats.
I have refinished many rifles and shotguns using this method and they generally come out looking better than new. Heck, My old .22 still looks great after nearly 20 years.
It is a lot of work and rather time consuming but it is a labor of love and something that will make you proud every time you look at that rifle.
I have refinished a few and used chemical stripper, and varnish removing pads, and tooth brush's to clean the old finish from the checkering, very little sanding is needed with this method, I use true oil on walnut,maple and laminate, you may need stain on the 788 as its likely birch or another lower grade wood.
Use Bix Strip to remove the old finish and then steam the stock to reise the dents and the grain. Then let it dry and lightly (LIGHTLY) sand with a very fine grit to remove the feathers. Then finish off with Tru Oil or boiled linseed oil. Do not, under any circumstance, use steel wool. It will leave very small pieces behind that will eventually rust and look bad.
With the stocks we've done we used chemical strippers. no use sanding to much, just wipe the stock down afterwards with something to remove the stripper...i think mineral spirits if i recal correctly.
After that if there are dents, my one rifle i got used had a few, take a damp cloth and an iron. put the cloth down on the area of the dent and lightly iron. it will help remove the dents. this worked good for mine. light sanding, if you wrap the sandpaper around a sponge it helps keep it more even without the chance of as much pressure from using just your hand and fingers. tack cloth good after sanding with very fine grit and stain once the stock is prepared. stain and light sanding. tack cloth. stain and light sanding then tack cloth. two or three coats of stain. i stress the tack cloth because it helps get alot of the light sanding off. then finish up with the final coat. for my rifle i used the truoil and liked the results. take your time and enjoy your project. i had fun and it makes u appreciate it that much more......just don't be afraid to use after its pretty haha
If you sand to remove finish, you are removing wood and will alter the fit of wood to metal,butt plates, trigger guards, etc. Jimsdad's got it right, also youngbuck3006. you'll be suprised what a steam iron or even a couple drops of water can do for dents and dings, once the finish is removed.