Automatic transmission fluid (atf) is similar to universal hydraulic fluid other than the chemicals added to make it perform in a specific transmission. Conventional automatic trannies are hydraulic pumps with clutches and other cool stuff but we're going to leave it at that. Universal fluid doesn't have a lot of additives so it costs less. I watched bullseye shooters use a concoction based on atf several years back, suspect they still do. Atf usually has detergent properties, if it helps keep trannies clean it may do the same with your reloading equipment. Keep it away from primers, it could have penetrating properties as well. There's so much chemistry in the petrochemical business these days I prefer to buy oils formulated to do the job at hand.
If you use up that whole 5-gallon bucket anytime soon I suspect you're using too much.
