I've been wondering for quite some time now, what were those flak jackets made of? What material provided protection?
I've seen them for sale in magazines for around $60. What is the intended protection level?
A flak jacket will only stop shrapnel, like from a hand grenade. They are pretty much ineffective against bullets.
Very high-tech ceramics. They are more complex than you might think. They must be lightweight and sustain multiple impacts.
This is one company that makes body armor: Ceradyne
Vests are made of layers of woven aramid fibers such as Spectra or Kevlar, these materials transmit the force of an impact to a much wider area and prevent penetration. The standard for the ability to stop bullets is called the NIJ (National Institute of Justice, IIRC) standard and vests are rated as to "Level", most police officers wear Level IIA or III, which will stop most (or virtually all, in the case of Level III) handgun bullets and shotgun pellets. More layers of fiber equals better protection, and more weight. That "four pounds" probably refers just to the ceramic plate, the whole vest is likely a lot heavier.
Military vests are Level III with front and back ceramic inserts that raise the level to Level IV, which will stop even "armor piercing" bullets. The ceramic plate has a plastic backing to keep fragments of the plate from penetrating the vest itself, the plate plus the vest is for all intents and purposes impervious to small arms fire, IF YOU HIT THE PLATE. The whole vest can't be ceramic, because of flexibility and weight problems, so there are gaps at the shoulders and under the arms.
The flak jackets from Vietnam were ballistic nylon and would help against grenade and artillery fragments, but were not resistant against rifle fire.
Second Chance is the company that developed the ballistic vest for police use, they have recorded something over 2,000 police officers whose lives have been saved by a vest, not only from bullet impacts but also in car accidents -- force is force, and force applied over a larger area is less force overall.
And to the pinhead wondering about why the government couldn't wave a magic wand and create a vest for everyone, no matter how much money the government throws at a problem, "the government" can't do much by itself. Dow Chemical has to make several thousand miles of Kevlar, another company weaves it, another company makes the vests and carrier, and yet another company makes the ceramic plates. These things take time.
Liberals are so posessed of magical thinking, it's sad really.