This is my first instructable, so any feedback (positive or negative) will be welcomed.
This is a spring loaded dart made of common items found in my local hardware store. My son and I saw something similar to this on a National Geographic special about the Chinese weapons. I don't remember what they actually called it, but from what I remember it was considered to be an assassin weapon. A low powered spring loaded dart that was typically dipped in poison. The weapon was easily concealed, and powerful enough to break the skin which in turn administered the poison. My version will shoot about 35 feet. I imagine that if I put a tip on the dart it would travel further due to aerodynamics.

Step 1: Material and Tools

Everything I used to build this was found at my local hardware store.

Parts Lists:

1 - Shut off valve with chrome sleeve
1 - Short length of 1/2" copper tubing (2-3/4" long)
1 - 1/2" copper cap
1 - Strike plate
1 - Washer #10 I think
2 - Set screws 6-32 thread 1/8" long
1 - Length of aluminum solid tube 1/4" diameter
2 - Springs (#11 at my hardware store)
2 - Bronze bushing (5/8"O.D. 1/2" I.D.)
2 - Bronze bushing (1/2"O.D. 3/8" I.D.) Not pictured sorry
2 - Bronze bushing (3/8"O.D. 1/4" I.D.)
1 - tube of Locktite

Tools:

Solder iron
Torch
Dremel
Hammer
pipe cutter
Various files
Drill
Allen wrench

Step 2: Construction Begins

First I used the pipe cutter to remove 4-1/4" of the chrome tube from the shut off valve.
Then I took the bronze bearings and slid them inside each other to make 1 long bearing with 5/8" O.D. and 1/4" I.D. I slid this bearing inside the chrome tube and soldered in place at the end of the tube.

Step 3: Working on the Copper Tubing

Take a piece of 1/2" hard copper tubing and using a pipe cutter cut it down to 2-3/4" long.
Solder on 1/2" copper cap to one end of the tubing.
slide copper tubing into the Chrome sleeve and tape it in place.
Drill a small hole 1/4" from the edge of the chrome sleeve going through both side of the chrome sleeve and the copper tubing.
Remove the copper tube from the chrome sleeve, and set the chrome sleeve to the side.
Using a dremel I cut an L shaped groove on both sides of the copper tubing.
The groove is 1-7/8" long with a 1/4" leg (Which creates the L shape) cut towards the where the cap is located. Then I filed the grooves smooth.

Step 4: More Work on the Chrom Tube

1-Tap the two hole just drilled into the chrome tube with a 6-32 threaded tap. Once the set screws are in place, the copper tube will slide in and out of the chrome tube as if it were on a track. the screws also prevent the copper tube from completely sliding out of the chrome tube.

2- On the opposite end of th chrome tube where the bronze bearings are drill a 1/16" hole through the chrome sleve 1/2" from the edge. Then I used a dremel to wide the wide the hole. The overall dimensions of the hole are 1/8" X 3/8". This hole will be used for the triger assembly.

Step 5: Trigger Assembly

The trigger assembly was originally made out of a copper strap hanger which you can see in the picture. The only picture of the final trigger is an installed on, but the old one shows the concept of how it works. I cut the trigger assembly out of a brass strike plate with a dremel, and then hand filed to the desired shape. Can you tell I like my dremel? The larger hole is 1/4" in diameter, and the smaller hole is 5/32" in diameter. The strike plate already had a curve end which I made the top of the trigger. I pushed it through the chrome sleeve, loaded a dart, locked it in place, and then bent the bottom of the trigger to lock it in place( I beat it with a hammer).

Step 6: The Springs

I wanted the springs 3" long so that when the brass tube closes into the chrome sleeve the spring will apply force against the bronze tube. Thus locking the copper tube into place by binding it against the set screws when turned into the leg of the L groove.

I kept 1 spring full length and I cut one down to make the total of 3".
On the full length spring I soldered on a Flat washer and a little piece of metal to fill the hole in the washer. I placed the springs into the copper tube, and then inserted it into the chrome sleeve. Once the copper tube was inserted into the sleeve I locked into place with the set set screws. I used locktite to prevent them the set screws form backing out.

Step 7: The Bolt

The bolt is a piece of aluminum 1/4" diameter and 2-7/8" long.
I used the dremel to cut a 1/16" groove into the bolt. the groove was cut 1/2" back from the front of the bolt. I chose not to put a point onto the bolt for safety reasons, but it could easily be done.

Step 8: How to Load and Fire

1 - Pull bass tube out of chrome sleeve.
2 - Put the bolt into the chrome sleve.
3 - Once the bolt is in the chrome sleeve lock it into place with the trigger assembly.
4 - Push the copper tube back into the chrome sleeve and turn it to lock it into place against the set screws.
5 - Point it away from people and animals.
6 - Push down on the trigger and watch the bolt fly.
No... Seriously watch it fly. My son and I spent 30 minutes looking for a bolt because we didn't see where it landed.

This is potentially dangerous; please use caution if you decide to build one of these. I am not liable for any injuries or accidents that may as a result of building one.