I always wanted to shoot steel darts (the type used for recreational dart games). However, this is not easy. Lots of hurdles. First, steel darts aren't made for shooting. Therefore you can't shoot them overly fast as the tips break on impact. Second, the fletching is very vulnerable, in fact not made for any kind of pressure. Third, they can be quite expensive.
I found some on amazon, at 40 cents a pop! Quite cheap, but they certainly do the job.
I made an experimental pistol with my idea of how to shoot them. Toothbrush heads to hold them in place, extremely prestretched rubber and a "pinching" method to keep the backside firmly on the string.
This works quite well, the darts fly 15 meters without any problems. They stick into anything they hit - wood, aluminum, plastic.
I think this can be optimized for more compact sizes, and probably with a pump action mechanism. I had to add string guides and work with the ideal string length a lot until everything worked smoothly.
The darts are not lethal I think, but a lot of fun to play with.Amazing, what 4 cm active band length can achieve! Also note that the band wear is very low, probably because there is no tapering, and the bands never touch anything.