My daughters 20ga 500 has an Undertaker choke and is shooting the 3" Hevi Magnum Blends very nicely at 30 yards. I didn't count holes, but it was a great pattern. Last year she shot the 3" remington #5's and they were satisfactory, but the Hevi is much better.
Be warned, those 3" shells pack a punch in that light weight gun. My daughter got rolled backwards for a flip last year when she fired with her feet up hill and leaned against a skinny tree. Roller her right over. We laughed till be cried, even though she missed the jake. I just have her practice with bird shot before season. She gets lots of cheap trigger time and no bruise. She did fire one 3" in practice this year and her arm went numb.