Back on topic, I've experimented with various snake loads over the years and I've never found them to be all that satisfactory. Regard less of the cartridge used, the patterns open up at ranges much over a yard and leave holes large enough to miss the head, and unless you get a solid head shot, you are not going to incapacitate the snake.

So if you use one, you need to get the muzzle in close - just outside striking range with a large snake - before you fire.