BLO is the industry dregs. Inhibitors are added for shelf life, driers are added so it might actually cure some day, solvents are added to reduce viscosity.
It has no place on any firearm. Even if you are looking to add it to old military arms. Go to an art or paint store and get fresh oil in a tiny container and replace with fresh regularly. More problems are caused by old garbage oils than just about anything else in the finish world.
Permalyn is a polyurethane, which is very different from urethane. It is a very average finish geared heavily toward ease of use. It is far superior to BLO for any and every application. They sell it in quart bottles, which is an insane amount for virtually any occasional stock maker to use before the oil gets old. Using any old finish is a recipe for a serious PITA.
