Large bore "sniper" rifles like the Barrett M82 / US M196 are worth mentioning in reference to the skills used by the shooter, but these rifles are not commonly used for hunting. Sporting purposes of these rifles includes some long range hunting of big animals, and target shooting. Many of the large bore rifles of this sort are specifically set up for target shooting and while supposedly capable of using standard military ammunition, the chamber tolerances are so tight that they will only function with specific match grade ammunition.
Military variants like the Barrett are actually not quite as accurate as the dedicated target rifles, but they tend to be more reliable and tolerant of military ammunition which was originally designed to function in heavy machineguns. These military rifles are primarily for precision destruction of material at moderate to long range. This can include shooting surface laid land mines with explosive tip ammunition in order to detonate mines from a safe distance, the destruction of specific enemy equipment and disabling vehicles. While it is next to impossible to shoot down a flying aircraft with one of these rifles, they are quite efficient for wrecking critical electronic and engine components on the aircraft while they are on the ground. They are also used by unconventional warfare units to provide long range direct fire support in defense of fixed positions and to disable enemy vehicles. These large bore long range rifles in general fill in something of a gray area between heavy weapons and regular firearms. With that understanding, the survivor should realize that these rifles have very little practical use but can be one of the very few commercially available weapons on the market which can hold some more serious significance on a battlefield.