The neighbor across the road tried a pellet rifle 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 rifle 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 rifle can do the job, and a whole lot cheaper.
In my situation it is more effective to trap and relocate.