The only time I experienced what you may call "rifle fatigue" was shooting hogs in texas with my .338 Lapua Magnum (22lbs) and having to drag a couple hogs with that beast slung over my shoulder through the cactus and Mesquite.
After reading this I can't get rid of the image of a sweating, giant of a man; emerging from a thick tangle of brush and cacti after having hiked two miles with a hog under each arm and a 22 pound rifle hanging from his neck. A super rifle for Superman!