Apparently it's as much to do with the ammo - Performance Ballistic Alloy, as they call it - as it is about the basic MV of the rifle.
Checking out the site it seems he was using this springer
http://www.gamousa.com/Catalog.aspx?Product=62
And this .177 ammo
http://www.gamousa.com//Catalog.aspx?Product=79