Flechette's in 12 ga shotguns were proven ineffective in Vietnam.
They are still ineffective in 2013.
Not true as the advances in steel shot technology has made flechette's a very effective armor piercing round. The federal law enforcement training center put out a video showing the effectiveness of these rounds and their armor piercing ability.
While buckshot is effective, it is the most over rated defensive load. It's only real advantage is being able to increase the probability of hits because of multiple projectiles. Each projectile on it's own is a poor performer.
Tell that to the Germans in WW1 as they proved so effective they threatened to put to death any Americans captured carrying them and tried to have them banned for use in warfare. I have killed game with buckshot and have personally seen it's effectiveness on human beings.