We're already there. These guys printed a lower receiver (legally considered to be "the gun") of an AR-15:
http://www.extremetech.com/extreme/133514-the-worlds-first-3...
Now you can't (right now) even with laser sintering produce some of the highest tolerance parts of a gun, such as the barrel. But we're getting there.
With 3-D printers, this can currently be done with only very simple products. But the capabilities are expanding...
We're already there. These guys printed a lower receiver (legally considered to be "the gun") of an AR-15:
http://www.extremetech.com/extreme/133514-the-worlds-first-3...
Now you can't (right now) even with laser sintering produce some of the highest tolerance parts of a gun, such as the barrel. But we're getting there.