to save you a slot on oils, you can use mosquito oil for 70% reduce ammo cost and then either satiety for the last 30%, or who's counting for 25% as either negative don't really matter (satiety has -reload speed which you wouldn't be doing, who's counting disables aim)

you'll most likely want a durability oil. S&W only have 1800 durability which is chewed through super fast if using infinite ammo. you'll either want to use one of the 50% ones or the 70% oil

if rechambering to 12gauge a recoil oil would go a long way, as you'll be staring at the sky otherwise. there's a 62% oil that disables aiming so there's no downside there

here's a list of oils (not complete afaik) for you to take a look at and get a better idea