If I remember rightly at approximately 15' with 00 buck it was about 4" to 6"
That's not exactly an aim anywhere pattern. A Remington 870 riot gun with 00 Buck (9 pellets) has a pattern ~24" wide at 25 yds. That's with no flyers. In competition, shooting at the B27 silhouette target it was very important to hold dead center as the silhouette is on 27" wide. IIRC it was 5 rounds in 5 seconds, hard to do with the recoil factored in. I just checked and they don't shoot that anymore so couldn't verify the time. All I remember is you felt like a puppet on a string and someone was jerking the hell out of it.