Number 4 for anything small. I found that Speer has released a 38/357 birdshot round. It has a 5 - 10 yd range. It looks very effective as a snake round. To see it in action go to Gunblast.com.
“I found that Speer has released a 38/357 birdshot round. It has a 5 - 10 yd range.”
You will be hard pressed to kill a snake much past 5 feet with those rounds. 15 to 30 feet is wishful thinking.