Blackdog,
Eric VonAshwege can probaly tell you more due to his experience with boats, but all the teak oils I have seen are sacrificial oils that must be reapplied several times during a season of boating. They do not "cure" or "dry" like you seem to be thinking. They just penetrate into the teak and form a UV and water barrier until the sunlight and water wash them away. On my boat I must reapply oil monthly to keep the teak from turning gray. There was one product Deks Olje which actially did dry like a penetrating varnish. But after 3 years or so it turns a nice opaque black and you have to scrape/sand the teak down. Too many sandings and your teak is gone! So I and every water rat I know went back to traditional teak oil that we lovingly reapply several times per season. I can't see how it would work on a gun.
Best Regards,
JMC