Actually, in this case Colin, you are caught by old knowledge in a world that is changing.
To say "Eskimo" or "Red Indian" is no longer proper. "Eskimo" people now call themselves by the correct name of their tribal lineage, which is "Inuit." Inuit is a lineage like Choctaw, Cherokee, Seminole, Algonquin, Apache, etc. As a group, the "Red Indian" is now called the "Native American." These name changes started in the last 50 years and have been slowly increasing in usage. Sort of like the difference between "Negro" and "African-American" and "black."
The other thing you mentioned that you don't understand is the meaning of Magnum - which for us actually is a reference to an oversized cartridge for a given bullet. When we talk of caliber in a gun, a hypothetical 1000 caliber gun fires a slug one inch in diameter. The "American Eagle" handgun fires a .50 caliber (= 1/2 inch = 12.7mm) slug.
From the "Dirty Harry" movies, the guns were .44 caliber. The slug was .44 but the cartridge was slightly larger because it carried extra gunpowder. Most cartridges that are cylindrical are NOT magnums. But if you ever see a cartridge that is bigger around at its base than the bullet it shoots, that is a magnum.
You mentioned a .22 gun by saying you had no feel for it. That size bullet is close in size to the 5.56 mm round. Not identical but close. Oddly enough, Cajun hunters frequently use a .22 magnum for hunting alligators. So "magnum" and "caliber" attributes can coexist.
You also expressed disbelief that we would depend on hunting for food, but you miss out on a couple of points.
First, we sometimes license hunters to kill in order to thin natural wildlife herds that are over-eating their pastures and thus finding reason to wander into inhabited areas and eat Aunt Jane's petunias. Or Farmer Fred's corn. This is part of wildlife management, an attempt to not kill off every species we could possibly eat.
Second, there are those people who enjoy being closer to nature than the impersonal, cold glass of a supermarket's freezer case.
Third, it is often cheaper in some parts of our culture if you kill at least some of what you were planning to eat rather than go out and buy it.