I have had good luck using Howard's Restor-a-finish. It is available from Lowes or Home Depot. It will disolve the grunge and surface finish without altering the color. You can get it with stain in it and I have used the Walnut on CMPGarand
Stocks to darken it a bit.
After cleaning the stock with Restor-a-finish, I hand rub several coats of tung oil finish like Formby's. Polish with 3m White pads between coats. Then wax the stock after that.
I have finished several stocks this way. It will not work with shellac.
Here is a CMP Special Grade Garand. It has a correct receiver, barrel and trigger group all dating to 1955. The bore measures .5. I redid the stock as mentioned above.
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