My doublegun is a 19 gauge. The barrels are choked IC/MOD. I took the time to pattern it at 25, 35 and 45 yards. 45 yards is too far to reliably kill something as small as a quail or dove. For the 25 and 35 yard patterns I tried #8, #7.5, #6 and #4. The #8 patterned best overall from both barrels for 25 and 35 yards. The Modified choke barrel has a strong preference for the #6 for some reason, but again overall for both barrels #8 was best. I use #8 for dove, quail, woodcock and rabbits. I experimented a lot with shot size and load components because I wanted to hunt turkey. Through a long day of trying different combinations, one really stood out. This combo is #6 with just 7 copper coated lead BB's dropped on top. I use this for squirrels, pheasants and turkey and would use it for something larger like a raccoon if that was something I hunted. Interestingly to me, I did the same load components with different shot size and the pattern was significantly different. I have two "loads" that work for me and I'm sticking to them but in the end the real conclusion was that the load components seem to make more of a difference than just changing the shot size with the same components.