I thought about this...
If you load specifically for snake, what do you do when you run across a non-snake threat? Like feral dogs, bear, cougar or feral sub-humans.
It just seems that unless you're in an area where poisonous snakes are the only thing you'll have to deal with, it would make more sense just to wear high boots and to load copper-plated lead than load snake loads.
But having said that - The S&W Governor probably is the utimate anti-snake gun.