This is a simple, less than 30 minute project I put together after one of the heads of my (very inexpensive) arrows fell off after constant stress on the head. I used a new arrow for the sake of demonstration.
DISCLAIMER: I AM NOT RESPONSIBLE FOR ANYTHING BAD THAT HAPPENS WHEN USING THIS ITEM. IF (NOT) USED PROPERLY, IT CAN RESULT IN UNSEVERE TO SEVERE INJURY. YOU HAVE BEEN WARNED.
Step 1: Get the stuff
All you need is a target-style, hollow arrow and maybe a pair of pliers.
For the darts, you need Q-Tips and a pair of scissors
Step 2: Assemble the stuff
I like to shoot the arrow first at a cinderblock or a brick to loosen up the head a little bit, and pull it out with a pair of pliers. Then, pull the knock out (not shown), and save both the head and the knock (for further use). Congratulations! You have successfully assembled an arrow blowgun!
Step 3: More stuff
The darts are as simple as the blowgun. All you need to do is cut the head off of one of the ends of the Q-Tip and you have a safety dart that fits perfectly into the barrel of the blowgun!