Any fluid made for the automotive application is just that, made for a specific application. ATF can be more related to hydraulic fluid as it doesn't have to deal with combustion gases like motor oils but does have to deal with heat generated from the slipping clutches. The slippage, or frictional coefficient, is determined by the makers specs to allow the clutches to slip at the right amount. To do that there are friction modifiers employed, most are phosphorus based and some are sulphur based or a combination of the two. Dextron which is used in the current GM transmissions, contains per GM spec, 2200 PPMs sulphur and 650 PPMs phosporus. In an enclosed transmission case and as a moving fluid there are corrosion inhibitors to make sure that everything doesn't corrode up. But on a gun as a placid coating and in free oxygen, the inhibitors never get to work. Would anyone like to guess what acids are produced from the sulphur and the phosphorus that are in the ATF? I strongly suggest, use at the risk of destroying your weapon. Short term usage- most likely no problem. Long term storage from season to season- problem. Gun oils are made for a specific use, why chance it when the correct fluid is available. It's not like it's too expensive as compared to your guns. YMMV