Pat, I used to shoot 45 ACP shot loads out of my Sig P220. I found I could kill a ground squirrel consistently about four to five feet off the toe of my right foot. That made it about six to seven feet away which would be a typical snake encounter distance.
But, I can't speak to the effectiveness of the smaller snot cartridges. I'm guessing though with the 38/357 shot shells you'd have to be right on top of them.
