One of the great myths of Africa is to use a 12 ga with buckshot for wounded leopards. The fact is that sometimes the pellets won't penetrate the tough chect muscles ! Better to use slugs .But if you have just one projectile use your rifle as cats are more sensitive to the higher velocity !
The biggest mountain lion I've heard of was one taken in BC last year -weighed 220 lbs ! Most of course are much lighter .Last fall I did see a red deer that had escaped a lion attack .Limping, back torn up and the other deer were very nervous !!
And Watson , bring your revolver !