stupid questions

i know i am probably gonna get flamed but i have some dumb questions that maybe you know the answer to

1. why hasn't anyone built a gatling shotgun? seems like it would be easy to do, and rem 870's are pretty cheap donor guns

2. why can't steel cases be reloaded? i don't reload, maybe someday ill start but as long as im pickng up brass why not pick up steel too?

3. why doesn't rain destabilize a bullet? i know that supposedly the bullet moves so fast that the rain is pushed out of the way, but what if the rain was exactly in front of the bullet?

4. i had a chance to shoot some .30-06 AP, the penetrators would punch through 5/8" steel plate about half the time. would that be enough to punch through a kevlar vest with a trauma plate?

answers appreciated