A pellet gun is not a humane kill. I gave up on super colibris as contact range dispatch too. If a gun will stabilize them the 60gr aguila 22 hits like a hammer, is quiet and slow. Any shotgun with light shot would be a preference if I was worried about stuff leaving the yard. My groundhog gun was a 22 pistol, 9mm pistol or a dog. Yeah Steve, a dog. I mostly killed groundhogs to keep my dog from hurting himself. He killed them instantly, broke their necks but he tore himself up pretty good diving under my truck to get one.
The 60gr 22,usually needs a fast twist barrel but I found that marlin microgroove does good with it. Or modern problems require modern solutions there can’t be a ricochet if there isn’t a bullet. 220 swift of a 40gr 223.
As Bob said, as far as general shooting, no worries out here (I hate the damn hop growers!). If this were killing them in the pastures I'd just use the .22 or the shotgun. As I said, my big worry is what's behind my target in this location. And I guess I can consider the shotgun for the backyard. The areas they are digging up are thankfully away from the lawn, in a 1/4 acre or so that I'm looking to turn into native grasses and plants. Right now it's mostly still weeds and dirt.
Steve kills rockchucks, no problem, but I am trying hard to give him an aversion to gophers, because my one neighbor up at my top pasture uses a combination of traps and poison, and he piles the dead gophers for the coyotes. I don't want Steve ingesting poison. I have a gopher lady for that top pasture, and she piles them up too (no poison) and Steve has gotten into those piles. I don't want him mixing up poison and non-poison piles. Really, I don't want himn eating gophers at all since he just barfs them up an hour later. Barney the barn cat usually helps a lot, bringing several per week to the door in Spring and Summer. Right now she doesn't seem to be catching as many and it shows from all the new mounds.
I'd still like to get a pellet gun anyway just because I don't have one, but I will give the shotgun serious consideration for the current issue.