The Basics
Ammunition is nothing more than smokeless powder contained in a brass case ignited by a primer. The ensuing burn rate of the powder produces gases, creating pressure. This pressure builds up, causing the projectile (bullet) to be forced out of the case and down the gun barrel.
Reloading manuals are nothing more than cookbooks with different load data for different components. Want to reload a caliber you have? Look it up and check out all your options. What powder and primers do you have? What bullets do want to shoot? You can find your favorite recipe in the book!
But remember, any change in components can spike pressure. Follow the load book and you’ll be fine.