From the included Readme: 

This is the first DD Liberator release, tested functional on 5/3/2013 and again on 5/5/2013.  Design tweaks included from EXP001 and EXP002 experimental results.
Changes from EXP002:
-Barrel locking lug filet added to reduce stress concentration
-.2" hole added to handle to allow assembly without screw.  AR-15 grips will fit, but need a .2" hole drilled .4x.4" from corner.  Or download DD's modified AR-15 grip.  This is done so you don't need a metal screw to hold the grip on.
-SN removed.
-Hammer body firing pin hole reduced to 140mils to improve firing pin concentricity on primer.
-Trigger stiffened.

How to legally assemble the DD Liberator:
-Print (ONLY) the frame sideways (the shortest dimension is the Z axis).  USC18 922(p)(2)(A)*: "For the purposes of this subsection (The Undetectable Firearms Act of 1988) - the term 'firearm' does not include the frame or receiver of any such weapon;"
Thus, you can legally print ONLY the frame entirely in plastic, even without 3.7 ounces of steel.  

-Once the frame is finished, epoxy a 1.19x1.19x0.99" block of steel in the 1.2x1.2x1.0" hole in front of the trigger guard.  Add the bottom cover over the metal if you don't want it to show.

-Once the epoxy has tried, the steel is no longer removable, and is an integral part of the frame.  Now your gun has ~6 ounces of steel and is thus considered a 'detectable' firearm.  So now you can print all the other parts.

-Print all the other parts.  
The barrel must be built up in the z axis.  
The springs must be printed flat on their side.  
The hammer body should be printed such that the firing pin hole is in the z axis.
The hammer should be printed on its side.
The trigger must be printed on its side.
The spring connecting rod bushing should be printed up in the z axis, to reduce friction.
The spring connecting rod should be printed on its side.
All pins should be printed on their side to take advantage of intralayer strength.


We'll build the trigger first.  Take the trigger spring and note that there's a very small lip on one side of the ovular hole.  This lip mounts flush to the trigger piece, and gives the spring enough clearance to not drag on the bottom of the inside of the frame.  The spring's free ends should point away from the trigger, towards the back of the gun.  Mate these two pieces, and then insert into the frame.

Next, we'll build the hammer subassembly.  Insert the hammer into the hammer body with the striking cylinder facing the front of the frame.  Insert the hammer pin to connect the hammer to the hammer body.  Now press both coil springs onto the hammer body.  When the hammer is cocked, the coil spring diameter should reduce (not expand).  Once both coils are pressed on, pull one of the coil eyelets behind the hammer, and then insert the spring connecting rod into said eyelet.  Rest the rod on the hammer.  Slide the spring connecting rod bushing over the spring connecting rod, then pull the other spring back and insert the spring connecting rod into the eyelet.  Pull the hammer back and make sure everything is working well.  Pull the hammer back and drop in the nail and then insert the firing pin bushing concentric to the nail's head.  This keeps the nail from falling out when the hammer is cocked.  Notice that one side of the firing pin bushing is chamfered... that side faces the hammer.

Next, drop the hammer into the frame.  Note that the hammer secures the trigger.  Insert three frame pins to secure the hammer body.

Finally, slide the grip onto the frame and insert the grip pin.  Your Liberator is now ready to go!

Before firing a barrel, we recommend heating acetone to boiling and treating the barrel for ~30 seconds to decrease the inner diameter friction, which increases barrel life from 1 round to ~10 rounds.  Note that we recommend printing multiple barrels and using each only once.  Swapping the barrels is simple and fast: rotate the barrel to release the locking cam.  Pull up on the barrel.  If the barrel cam broke, turn the Liberator upside down to remove the debris.  Then drop your new barrel in and rotate it until it locks.   


*http://www.gpo.gov/fdsys/pkg/STATUTE-102/pdf/STATUTE-102-Pg3816.pdf