Ok, Here is my recipe for a WATERPROOF finish, and it ain't PC but it will work and work GOOD!!!
First, coat you dewhiskered and stained stock with Thompsons Water Seal, inside and out, real good, let it soak in and wipe it off. Let it dry and do a second coat
Second, Mix TWS with Formbys Low gloss Tung Oil 50/50 and give the stock two more coats inside and out letting it dry between coats
Third, give the stock a final coat of straight Tung oil inside and out, wipe it off, let it dry.
Fourth, give the out side finish as many hand rubbed coats of straight Tung oil as you care to apply.
You will have a completely water proof and original LOOKING finish,,,, who is gonna know?
...Ed