Remember though in a shotgun use birdshot, birdshot, slug. Body armor will not stop the slug.
To use gamer's parlance, such weapons ignore most soft body armor, especially when supplied with M2 AP bullets. There are exceptions, but they are heavy, expensive and uncommon.
I must respectfully disagree about shotgun slugs penetrating body armor. Common class IIIA armor will resist 12 GA shotgun slugs.