
A hunting rifle is a hunter’s main tool for medium to large game. It is for small game and fowl that a shotgun approach is better, it reduces the kill range, but even a small caliber bullet would pretty well devastate a duck or a rabbit, which takes away from the enjoyment of bringing home the trophy. Small game aside, a rifle is the tool of choice for bringing down your quarry.
The caliber of hunting rifles has actually gone down in the last century. Marksmen in the post civil war era noted that a smaller, lighter bullet with a higher rotational velocity was more accurate than a large heavy bullet. The earliest rifles had a caliber of .56, which is just over half an inch. Compare that to a modern rifle, where a .22 cal is fairly standard, and a .45 caliber round is considered large.
The only reason to use a larger caliber in hunting is if you plan on taking on a heavily hided type of game. Elephant hunting, though illegal in most countries today, was the prime example of a large caliber hunting rifle used on game that required it. The elephant gun found military applications in World War I, as it was used against infantry shielded by metal plating, as well as on lightly armored tanks.