[speedybird]

> For the ghost guns, do you still need to have professionally manufactured elements standing pressure, like a barrel,

Yes, the 'ghost guns' politicians fear the most are built like that. Particularly, AR pattern rifles that have printed or home-milled receivers but are otherwise build out of factory parts.

There are also some 'ghost guns' that are wholly homemade, with all the variable quality you would expect. Most of them are probably more dangerous to the user.