Generally, steel shot shoots full choke patterns in modified barrel, and modified patterns in improved cylinder barrels. But it can vary some - certain guns with certain shotshells can shoot considerable tighter or looser. Sometimes, it almost doesn't make sense.

For instance, my Browning Superposed is choke light modified and improved modified. Out of the light modified (top) barrel, it shoots about 53% with Federal Dove and Quail, and about 57% with Remington Duck and Pheasant. I also have a Super X Model One with screw in choke tubes. Using the light modified tube, it shoots about 56% with the Remington Duck and Pheasant. But the Federal Dove and Quail only print 36%. I have to put in the full choke tube to get it over 50% with this load. Go figure . . . .