Parts:
Cardboard
½†thick scrap wood
Click pen spring
Tiny extension spring (I got mine from a printer)
Rubber band
Pencil
A couple 1/8†thick nails
Tools:
Hot glue gun
Razorblade
Scissors
Pencil
Band saw or scroll saw …...I guess you could use a hand saw.
Time to start:
Cut out a bunch of these gun shapes:

Now, cut the trigger out: (I used cutting board but wood would work)

Drill a 1/8†hole in the center and glue the click pen spring the back of the finger-part.

Now make the catch:

Attach the catch and trigger to the gun body. Make sure the edge of the catch just barley overlaps the trigger. Also, add a small scrap of wood in front of the trigger to stop it from moving too far forward.

Glue on the first layer of handle spacers:

Then the next layer:

Finally , the last layer of the handle: make sure to glue the trigger spring to the bottom and top handle spacers.

Glue on the first of the barrel spacers:

Add the next two layers of the barrel:

Make sure a dart fits loosely in the barrel:

Add a piece of cardboard to look like the hammer:

Next, add some support for the trigger stop, and also for the dart:

In another main body piece, poke some holes which line up with the nails for the trigger and the catch:

Cut slots which run almost the entire length of the gun: (they should be wide enough for a pencil)

Glue the second body panel to the rest of the gun:

Cut your pencil until it protrudes about 3/16†from either side of the gun and notch both ends:

Take your rubber band and stretch it over the front and connect it to both ends of the pencil:

Add a couple scraps of wood to the front to keep the pencil from ripping/smashing the cardboard:

Here are a few pictures of the complete gun:


