I have a 6mm remington (same bullets different case)and NOTHING has come close to the bergers for accuracy, I use them on coyotes and smaller. they aren't designed for hunting so I use barnes X for deer, antelope, not as accurate but great terminal performance. With marmots accuracy is all you'll need to worry about. Also, I think the heavier grain bullets will be better(90grains and up), as they will be affected by the wind, or other weather factors.