In the Hollywood BOA incident, one cop with a shotgun was about 80 yards from the bad guys, directly across the boulevard, taking cover behind a kiosk. He got off several solid shots from his 12 gauge, which had zero effect due to the bad guys’ full body armor. The bad guys then riddled the kiosk with AK rounds, which went right through it, wounding some officers.
In the exact same situation, a .223 instead of a shotgun would have penetrated the bad guys keflar body armor and probably would have ended the incident long before the SWAT guys showed up.
This of course was after many rounds had bounced off center mass, slooooow learners...