John,
Just before bed last night I found a short section of electrical conduit, to short to be taken seriously. I was disheartened to find my cheap dime store marbles I use for sling shot ammo to be a smidgeon to large, but then noticed on of the kids "Nerf" gun darts the cats had been playing with. Fit perfect and the kids and cats all got chased to bed in style. A weird style, but style.
After they had all cleared the common areas of the house I ran across an insulin needle in its carrier. This also fit perfect and at the short ranges I used my short tube hit pretty hard and front forward. I am considering rounding up these things as they get used and drilling the tip enough to glue in a wire nail with the head snipped off and finding a five foot or so tube.
In the way back a friend saw an article on these things and "made one" from a copper pipe he had. He used a large punch he heated up to form cones from a plastic milk jug, cut those to fit, straightened and stiffened some small copper wire (lock one end in vise, other end in electric drill chuck, pull and bump the drill on a few quick times, twisting both straightens and work hardens the copper wire) Until he last the last of his darts and decided he had better uses for his time than making new ones, there were dart perforated soda cans, telephone poles and trees all over the neighborhood.
Also as a kid I saw a demonstration at "Unto These Hills" of a Cherokee using a section of American Bamboo with cat tail (bull rush) darts. I would have thought the bore to big, but he made it work.
A friend that played with one a bit gave the main character of his first SF&F book a blow gun as his main distance weapon. At the time despite youthful experiences mentioned above I felt his unicorn in the book more believable than the feats his main character performed with his blowgun.
-kBob