what is the volume of 500 0.080" pellets?

If 0.08" is the diameter then

Go to this page on this site - It is under formulary.    (the formula is there plus it will workit out for you.

 http://web2.0calc.com/formulary/math/geometry/sphere

Put in radius = 0.04  (half the diameter)

Get you answer.

Multiply you answer by 500

and that is you answer in cubic inches.  

Are the pellets round?

 Is 0.08" the diameter or the radius or what?

Indeed, I should have said spheres.