Cylinder bore can be thought of as a choke, just like any other. Like other chokes it has a purpose - in this case it is to throw a broad pattern of shot at shorter distances. With 1 oz. of 7 1/2 shot a 12 gauge cylinder barrel can produce a nice, smooth pattern out to 25 or even 30 yards. Another way of looking at it is that a cylinder bore will put approximately the same number of pellets in a 30 inch circle at 20 yards that a full choke will do at 40 yards. For closer flushing game birds, American skeet and some presentations in sporting clays cylinder bore can be close to ideal. With well made shells and number 6 shot or smaller, a cylinder barrel can produce very evenly distributed patterns. Do not discount the usefulness of the cylinder bore - after all, until about 1866 or so it was all anybody ever used (and those old boys seemed to bring home the bacon).
Sharptail