Hummingbird Gen 2 Build Guide


 Part Quantity
Filament 417g
AR-15/M4 Compatible Grip 1 pc
Mill-spec Buffer Tube Stock 1 pc
Kepler Flywheels 1 pair
Out of Darts Krakens 1 pair
Neutron Compact Solenoid 1 pc
Out of Darts Motor-Spanning Board 1 pc
Button Microswitch 1 pc
Mini Microswitch 2 pc
XT-60 Male Connector 1 pc
18 AWG Silicone Coated Wire Some
Heat Shrink Some
Adjustable Clevis Pin 1 pc
3mm Dowel Pin, 45mm Long 3 pc
3mm Dowel Pin, 36mm Long 3 pc
3mm Dowel Pin, 30mm Long 2 pc
3mm Dowel Pin, 20mm Long 1 pc
2.5mm Dowel Pin, 14mm Long 4 pc
M3x16 Flat Head Screw 4 pc
M3x10 Flat Head Screw 4 pc
M2x4 Flat Head Screw 4 pc
Long Compression Spring 1 pc
Short Compression Spring 1 pc


All STL files come with the models in their proper print orientations and will print without supports. Some files may need to be rotated around the Z axis to fit on the bed area.

The longest part is the top, which is 253mm long. If printed at a diagonal, the bed needs to be at least 200x200mm. The tallest part is the receiver at 208mm long. In total, the smallest printer build volume needed is 200x200x208mm. 

Recommended settings are 200micron or smaller layer heights and 1.5mm shell thickness. 


Install the motors to the motor mount. Use the instructions on the motor-spanning board to ensure correct orientation. The two prongs that had touched the print bed point toward the user. Secure using two M2x4 screws. 


Using the motor support tool and flywheel shim, install the Daybreak or Kepler flywheels to the motors. 

Remove the flywheel shim

Install the motor-spanning board according to its documentation. 

Assemble the rest of the blaster's circuit. 

Install the AR-15/M4 grip using a 1/4x28 screw. 

Install the magazine release into the receiver. Optionally, silicone grease may be used to ensure smooth operation.


Using the small compression spring and 3x30mm pin, install the magazine catch into the magwell and magazine release. 

Install the switches using the one 3x20mm and four 2.5x14mm pins. The mounting holes on the switches may be slightly undersized. If so, they may be reamed out using 2.5mm and 3mm drill bits to allow the pins to fit easier. 

Using the long compression spring and two 3x36mm pins, install the trigger. It may be necessary to apply silicone grease to the contact areas of the trigger for smooth operation. 

Install the autosear and fire control group cover. 

Install the pusher and pusher flap onto the solenoid. Note the pusher pictured here is a prototype revision; the actual pusher will look different. 

Install the solenoid and side rails using four M3x16 screws.

WARNING: Ensure all four screws used here are the M3x16 screws. Using any of the M3x16 screws later to secure the top of the blaster may destroy the solenoid.

Ensure the pusher is oriented with the flat face upwards and that the back face rests against the front of the solenoid body. 

Thread the battery connector through the hole into the battery compartment and install the flywheel assembly to the front of the receiver using an 3x45mm pin.  Ensure wires go through the proper channels and are not pinched. 

Install the barrel using an 3x30mm pin. 

Install the handstop using a 3x36mm pin.

Install the top using four M3x10 screws. 

WARNING: Ensure that all four screws are M3x10 before securing the top. If the M3x16 screws are used instead, they made destroy the solenoid. 

Install the top rail with the chamfered end towards the front of the blaster. 

Install the buffer tube using two 3x45mm pins. 

Install the stock. 

Install the foregrip using the clevis pin. If sourcing entirely metric hardware, the hole may be widened to 5mm using a drill and the clevis pin may be replaced with a 5mm diameter pin. 

Assembled Blaster