I'm so new into reloading it's funny.  I'm looking to stock up on supplies to stock up on while I save money for a reloading machine.  I've got two 5 gallon buckets of 9mm brass from my many trips to the range and now I want to primers.  I've been told to get Federal 100 small pistol primers, but with his Godhood celebrating his second term, the 100's are hard to find.  Can anyone tell me the difference between the 100's and 200's?

nc19

Same physical dimensions, but as OB mentioned, the 200s are magnum, the 100s are standard.  They differ in the amount of brisance http://en.wikipedia.org/wiki/Brisance they contain.  Check your loading manuals carefully, and use the right ones with the right powders.

You can have everything from squibs to overpressure rounds if you use the wrong combination of powder and primer.

Primers have more "boom" than folks think. That's why it's critical to be using the right ones.  I saw a primer only load in a 44 magnum stick the 240 grain slug 3 inches down the barrel of a revolver once...