Wider than a .224" bullet that's for sure......
Look at the buckshot patterns at 12 feet.
https://www.theboxotruth.com/threads...-patterns.327/
Now add 8 more feet......
Again I'm not advocating a shotgun over an AR15 in all cases. But many of the myths about shotguns are just that, myths. A shot gun is a formidable weapon at close range inside 4 walls. When you get outside the 4 walls of a house for example, its usefulness diminishes with each added yard. I carried a Win Model 97 in RVN during boarding parties when searching junks for contraband. I could have carried a M16, but the M97 was better in close quarters.
Having both at hand is good to have another tool for the tool box.