Chart 1 Percentage Of Shot Inside 30" Circle CHOKE 20 Yds 30 Yds 40 yds Cylinder 80% 60% 40% Skeet 92% 72% 50% Improved Cylinder 100% 77% 55% Modified 100% 83% 60% Improved Modified 100% 91% 65% Full 100% 100% 70%
Based on this chart a 30 yard shot the improved cylinder will provide 77% and a full choke at 40 only produces 70%. Therefore, it should be good at 30 yards and under, but you need to pattern it to see what your gun actually does. I would suggest #6 shot for a more dense pattern and they have plenty of energy to make a clean kill at 30 yards.

Buy some turkey head targets (Cheap) which have instructions on patterning your gun safely and efficiently....