Bullets range from .17 to .50 caliber for cartidges. Black powder and shotgun slugs get even bigger. Bullet size is measured either as a fraction of an inch or millimeters. A .30-06 has a bullet about .30" wide, an 8mm Mauser bullet is about 8mm wide. Bullets come in many different weights and shapes, as well as sizes. I suggest you try a web search in Google or Dogpile using key words such as bullet, ballistics, caliber, nose, and other related terms. I am sure bullet manufacturers like Speer and Hornady have a lot of information on their websites. Use key words like speer and bullets or hornady and bullets. Search engines are great for getting info like this. Dogpile is at
www.dogpile.com . Google is at
www.google.com. Once you learn how to use the search engines, you can find out almost anything.