THEHOMEGUNSMITH.COM

Which provides information, including plans, on how to build things such as 9mm submachine guns out of standard steel tubing. Seems that the British feller (yes, BRITISH) who ran the site up and died here a few years back, but other people are keeping the site up.

Take it for what it’s worth: there are posts written there (such as this) that describe the experiences of Brits who did no more than simply download the instructions from this site. If they are to be believed, apparently the British police see downloading a PDF file from a publicly accessible website as sufficient cause to raid your home. So, FYI.

Also: you can buy the guys book from Amazon (the reviews are positive):

And there’s also this:

And this:

And this:

The point being: guns are not exactly rocket surgery. Couple these sort of home-workshop guns with rapid prototyping, and pretty soon some pretty quality sub-guns will be just a few hours work away.

Disclaimer; all the books say that they are for academic study only. Don’t you dare actually make a gun. That would be naughty.