I have been hunting Grouse for the first time with no. 7.5 and no.6 both in 2 3/4 shell and they were relatively easy to kill at 20 yards or less. The problem was when I was shooting between 20 to 40 yards. I was not able to kill any grouse, I failed 3 of 3 when they were not moving... with an improve cylinder choke.

Should I use 3 inches shells for the distances between(20 to 40 yards)?