You can't be real.

I Can't believe that a high school student would be doing a paper on "flechette" rounds for a high shcool paper.  In my Company (M Co. 3/11th ACR) we had two types of round.  Green rounds were full of cylinders about as large as your little finger, these we used to blow back bamboo or large obstacles.  Black rounds carried hundreds of little darts that we used against personnel.  These rounds, when used properly, would make hamburger out of enemy personnel.  These rounds were produced in 90 mm.  That being the size of the main gun on our Patton M-48A3's.  The reality of the round is something I don't think you ever want to experience.  T.V. does not portray the smell, the carnage of what these rounds wreak.  If this question is truly part of a school project then I challenge you to interview an armor or artillery veteran who has seen these rounds in action.  I had the misfortune to be involved in a night attack against a Fire Support Base where the 155 HOW battery went 0 deflection and fired beehive rounds against the oncoming enemy.  The next morning we peeled the NVA out of the trees for our body count.  They looked like they had been nailed by an air hammer, something that came into being years later.  Hopefully this will help you with your paper.