Electric Cross Bow

http://www.google.co.za/search?sourceid=chrome&ie=UTF-8&q=electric+crossbow+youtugbe

http://www.youtube.com/watch?v=BSjCY2kGyfI

http://www.youtube.com/watch?v=0R9u2gjbw1w&feature=related

http://www.youtube.com/watch?v=xLMd_B5bJU8&feature=related

http://www.youtube.com/watch?v=0R9u2gjbw1w&feature=related Note design, can automate using electric pulley

http://www.youtube.com/watch?v=4DaD_HGBoWw&feature=related home made repeating cross bow

http://www.youtube.com/watch?v=Yrv3nmOcv5M&feature=related home made bolt actions with 3D cad files and three step video tutorial on building it.

steel ball
http://shoottech.com/Page/Web/AR480MARKII