I got to thinking, that is, rethinking and after thinking about it, I think I understand Shakari's reasoning for the .500. I might be a little slow on the uptake, but I think I got it now...

A couple years ago I put a shot into a deer's head thru the mouth with a 140 grain bullet from a 6.5 Swede from about 2 feet. The bullet came apart in the jaw and teeth and never made it to the back of the head. This same bullet on another deer that had been wounded by someone else took the fleeing animal from a range of about 15 paces up thru the ham, breaking the back leg and coming to rest high in the chest on the far side, excellent performance, really. Same bullet.

I'd be delighted to use this combination for a shot at a cat in a tree over bait.

But...

Picture the leopard scenario with the cat facing you and my experience with the 140 and the deer's teeth closes the book on what I think about light calibers and charging leopard.

A leopard without his teeth still has four ways to cause a bit of consternation.

Thanks for the discussion fellows. Interesting stuff.