Most body armor is NOT designed to stop rifle rounds if it is rated below Level III, although Level III ammo will stop some rifle rounds like .223 and 7.62 and do a good job against shotgun shotshells. Keep in mind, that is for normal FMJ ammo and not armor piercing ammo. Below Level III are IIIA, II, and IIA. Forlighter armor, many have a center chest and center back pocket for an additional plate that will help disperse blunt force trauma over the heart (which can be stopped by such trauma), but also stop most rifle rounds.
Level IV and some special-made body armor will handle those calibers, but they are heavier materials and most likely have heavy plates. Many of the SWAT type law enforcement groups use armor rated at Level IV. Level IV armor will protect against armor piercing ammo.