I would like to build Lego projectile weapons. Are there any designs available? Can one make an amunition magazine and self-reloading mechanism? Should I use rubberbands as ammunition or are there designs that fire Lego bricks?
There are some Books available that include building-instructions (i don't own one of these, but i would choose the most current):
- The BrickGun Book (Book released in 2013, site has occasional updates as of December 2018 with more instructions)
- Badass LEGO Guns (December 2010)
- Weapons for LEGO Lovers (February 2009)
- as Joubarc said the at least 4 years old Forbidden LEGO (July 2007)
to answer your question about magazines/reloading mechanisms: see this youtube-video that shows such a mechanism in detail (although it's a bit hard to perceive details).
in addition the book about LEGO Technic Simple Mechanics might also be interesting for you, if you want to try building a own gun instead of just "copying" from a detailed instruction.
There is a book called "LEGO Heavy Weapons" by Jack Streat which is published by No Starch Press and can be bought for about £15 on Amazon.