I seem to do the best with guns that have some choke; choice for Grouse might be .002/.004. That and longer forcing cones seem to produce most even and productive patterns. As distances increase, a bit more choke is good as with IA & SD Phez, P Chics, etc. For that type of upland bird .010/.020 is about max needed. Agree that .030/.040 is generally overkill and contra-productive.

A Springer Spaniel, a 6# double and a fair day to hunt.