From experience on furniture, enough BLO will waterproof wood. If it's rubbed in with steel wool between coats, and built up until it no longer soaks in, and forms an oxidizing layer above the wood, it seems to do an ok job. That takes a lot of time though. I suppose the old military dipping in hot BLO accomplished the same objective- fill most of the exterior of the stock with oil,and then let it oxidize hard.
I prefer so called "wiping varnishes" on walnut/birch/beech/maple and most other stock woods.
I just used Watco's "Danish Oil" wiping varnish to finish and seal a Marlin barrel channel that I relieved to allow the barrel to float. Their "Teak Oil" is probably superior for weather resistance/sealing,but I didn't have any of that left over from furniture projects.
Polyurethane and spar varnish are probably better sealers, but they build up thick on top of the wood; something I don't want in my barrel channel.