Most of the snake hunting Ive done over the years (we used to get rattlesnake permits to find them, check them out, and enjoy the outdoors) was done by hand. If you are killing boa constrictors, pythons, anacondas, etc then even a .22 to the head will stop them cold, snakes are rather easy to kill, and are vulnerable to predators easily unlike what action and scifi movies make them out to being unstopable monsters.
Heck use something bigger if you want, the skins can be worth alot to leather makes. Also snake skins are easy to harvest, and snake tastes good (used to eat alot of them in the south, but up north there are very few left, I leave them alone to live their lives and do what nature designed them to do).