The story of the flechette (little arrows) goes back to the First World War when it was first utilised by the French. There is a very good piece that was done on the whole flechette program on THE GUN ZONE. It is by Daniel Watters and is a summary of the history of the project and you can also find the military research HERE

   BALL                      PROOF

   DUMMY                 ANODIZED ALUMINIUM CASE

   DUMMY                

Although I do not have any specimens in my collection, this is an AAI drawing showing four proposed designs of a tracer fléchette. The cartridge used in the tests was loaded with a variation of the one at top.