Let's talk quality.

I have used Buzz Bee blasters and others and they (obviously to me) lack the quality of Nerf blasters. I know that there are different materials, but does anyone know what kinds of plastics, foam, springs and other things that make Nerf better? I am looking to mod my Nerf guns, but don't know what materials to use. I am also curious about the materials of the Nerf line.

TL;DR: Any plastics/metals/foam/Nerf experts out there that can explain why Nerf is awesome.