re 3) the only regulated (in US) gun part is the lower receiver which looks like this: http://www.thingiverse.com/thing:11669 http://www.thingiverse.com/thing:1

re 3) the only regulated (in US) gun part is the lower receiver which looks like this: http://www.thingiverse.com/thing:11669 http://www.thingiverse.com/thing:11669 A mill is the right tool for that (though, it's tricky and some manual work will be required) A barrel is available for online purchase (in US) No problem here. For other countries, with stricter gun regulations, like Russia, making a barrel would be a problem, but it's usually solved with a Deep Holl Drill (using a steel rod or cylinder as a source)