Some people call rifle cartridges "bullets," but in reality the bullet is just part of the cartridge. A rifle cartridge is a case that contains primer, gunpowder and a bullet at the tip. The primer's job is to ignite the gunpowder, which in turn propels the bullet down the rifle's barrel and out to your target. The casing of the cartridge stays behind -- depending on the rifle you're using, you'll have to expel the spent cartridge manually or the gun will do so automatically.
If you thought choosing a rifle is a daunting task, you might be tempted to give up when you see the variety of cartridges on the market. To add to the confusion, not all cartridges follow the same naming conventions. In general, cartridge manufacturers name their product by bullet caliber -- the diameter of the bullet. Cartridge manufacturers in the United States use the English system of measurement -- almost everyone else uses the metric system.
Sometimes there's a second number in the cartridge name that can confuse matters. With some cartridges, the number refers to the length of the cartridge casing. But for black powder cartridges, the number tells you the size of the powder charge. The size of the charge tells you how much power the cartridge will exert on the bullet, which in turn tells you how fast and far the bullet will travel.
In addition to caliber, we classify bullets by weight -- measured by grains. One ounce is 435.7 grains, so a 150-grain bullet weighs a mere .34 ounces (9.6 grams). Lighter bullets tend to be more accurate over short distances but have less impact on distant targets than heavier bullets.
For small game, you can use small-caliber bullets. Cartridges for either a .17 or .22 caliber bullet are a good choice. But you also have to consider how much power you'll need to propel the bullet. Think about the distance at which you'll be hunting. If you'll be closer than 100 yards (91.4 meters), you could use a .22 Long Range cartridge. For greater distances, you may need to consider a .22 Magnum cartridge. You'll need to research cartridges designed for your specific style of hunting. Using backward induction, once you've determined the cartridge that's appropriate for your type of game, you can look for rifles capable of firing that type of cartridge.
If you want to hunt larger game, you'll need to use bigger bullets and cartridges with a more powerful charge. For medium or large game, you should look at rifle calibers ranging from .24 to .45. You'll also need to make sure the cartridge is powerful enough to fire a bullet with the impact force you'll need to take down the game you're hunting. Keep in mind that more powerful cartridges will have more recoil.
Okay, so you've done your homework and you know what kind of bullet and cartridge you'll need to hunt the game of your choice. That tells you the caliber of rifle you'll need to purchase. But what else do you need to consider? Let's take a look at what differentiates one rifle from another in the next section.