This 1.25 Kjoule DIY Coilgun can really cause damage. It took 2 years to conceptualize and develop. Nice thoughts put into the design. Just hope that it is for good fun and not any other things.
If you watch the video, you can see he uses 4 capacitors to store the charge, a 2000mAh NiMh High Drain battery and an old battery charger regulator circuit to avoid over charging.
Watch the destruction in the video.