The neighbor across the road tried a pellet r**** on the marmots after a couple of his dogs were ripped up requiring vet care. I don’t have the particulars on the gun he used, but he gave up the hunt when the r**** he used wasn’t effective.
There are pellet rifles that are big game effective with larger calibers and higher velocities, but I doubt most of us would spend the big bucks to buy one. I want one, of course, but a .22 r**** can do the job, and a whole lot cheaper.
In my situation it is more effective to trap and relocate.