I used to carry a 22 Mag derringer w snake shot upper barrel and JHP lower barrel. (for the bipedal variety snake) The performance of snake shot was disappointing & effective range barely outside strike range.
I w go w 38 snake shot - more shot is a good thing !
I am amazed you got away w stepping on one during the day. In AZ, they try to stay in the shade during the day but they are deadly fast. We used to hunt them at night - being cold blooded, they are really slow and like to lay out on roads as they retain heat. You can walk right up to them - you can see they really want to bite ya but it takes them a while to coil up and until they do, you can do anything you please. Very bony critters, not good eating IMHO.
Yes, they are valuable part of ecosystem but I still don't like them and if they get in my way, I will shoot them w/o hesitation or reservation. Nothing goes to waste in the desert, other critters gotta eat too - dinners on me...