Boiled LInseed Oil won't damage metal. It will dry on metal and be a pain to remove, so wipe the oil off any metal surfaces before it dries. Before adding the oil, sand the stock to whatever grit you want (220 at least) and wet it to raise the grain and then dry and dewhisker it a couple of times. Once it's sanded and dewhiskered, wipe it down with Mineral Spirits and have a good look at the wood surface. Mineral Spirits will show up any big flaws. If you like the look of the wood surface, let the Mineral Spirits dry and then add the BLO. Just put plenty of the BLO on the stock and let it soak in and add more as you see areas on the stock soak up the oil. When it won't take any more oil, you're about done unless you want to add some more the next day.
And remember...DO NOT wad up any linseed oil soaked rags or paper towels and throw them in the trash. Either lay the rags flat to dry or put them in a container full of water. Spontaneous combustion of BLO soaked rags almost burned my garage up once. I had an attack of stupid and was lucky to not get punished for it.