...i'll admit i use birdshot..
its my practice munition too, 7.5shot for 3.88/box of 25
at 5yds with my 18" cyl bore bbl, the spread is under 2.5inches--i'm not an expert, but thatll put the hurtin on any bad guy..
i keep two rounds of buck at the end of the tube in case the birdshot didnt do the trick...and a round of slug on the buttcuff...just in case..
EDIT: it was more like 5yds