homework and exercises - Concerning railguns and magnetic fields

I'm part of a group working on a Physics II project based on electromagnetism, and my group decided to create a proof-of-concept railgun, shown here:

http://www.doityourselfgadgets.com/2013/10/homemade-railgun.html

Instead of creating the full approximation of a railgun (since we were short on time), we created the small one consisting of a battery and aluminum foil rails. In that article, the author uses small, round magnets on the ends of the metal rod in order to "amplify the effect." However, my group and I can't really find any definitive answers as to exactly WHY this amplifies the effect and causes the rod to move faster. Can anyone help out with some answers or thoughts? Thank you!