The x40 (objective) is fine and the 10 power maximum I would say is a good choice for a .270
You would be good out to 200 yards with the right cartridge/bullet. Maybe even 300 yards, depending on how accurate the rifle is and what you are shooting.
The smaller the target (woodchuck) the more accurate you must be in order to hit it. The side of a large buck at 300 yards gives you a bit more "wiggle room" however, you still want to make a well-placed shot that is humane and will drop the deer DEAD pretty much within 20 yards or so from where you shot it (if not right in his tracks).