For Showman... like most, the first oil I was exposed to as a kid (age 73 at present) was 3 in 1 oil - all those years ago. Over the years I learned that there are much better choices than 3 in 1 - for almost any purpose. The moment you apply it you're golden - but over time it evaporates leaving a sticky film - that in a year or two will begin to turn into varnish... At least that's what years of tearing down and repairing fishing reels of every kind in quantity has taught me. You note that your shotgun needs "a drop" on action points and that otherwise it gets stiff... That's what 3 in 1 does... Any good quality gun oil (Gunslik, BreakFree, Kroil, are a few I can recommend) will perform far better -particularly as they age on whatever mechanism you're trying to keep working properly -firearm, fishing reel, etc.
At least that's my take on it. Can't remember how many "miracle repairs" I've done - just by using mineral spirits (paint thinner) and some elbow grease to remove nasty gummed up 3 in 1 residues on one item or other - then just a drop or two with good quality oil to get it working properly again...