Ekka, the specifics can be found here:
12 guage Line Launcher
The distance has to do with powder load and pressure developed. I'm toying with the idea of using a full load, and just pouring the shot out without messing with the internal wads... hmmmm
we'll see =) Definitely a helmet, goggles, brick wall, etc, for that one! lol It'd make it sooo much easier though... no more messing around modifying loads.