It all depends on the typical range at which your shots are taken. My grouse coverts are very thick. A ten yard shot is common with about 25 yards being the maximum before winter. Any choke at all is a handicap in my coverts. The first barrel of my grouse guns are IC but I shot a 16 bore for years with a cylinder bore. With an ounce of 9’s, no grouse could fly through my patterns up to about 35 yards. I patterned the gun at all typical grouse ranges and so I knew what the gun would do. One of the reasons I have been so successful with #9’s is that you can shoot open bores and still have enough pellets to fill out the pattern at the ranges my shots were taken. Go to a 7 ½ or larger and you can have gaps in the pattern at the further end of grouse shots. An ounce of 7 ½ contains 579 pellets while an ounce of 7 ½ contains only 346. It makes a big difference when the tight cover stops many of the pellets from reaching the bird. The old time grouse hunters knew this which is why they shot fine shot.
Not every grouse covert is like mine are, especially in the west. There the shots at grouse are typically longer. My average shot at grouse in Saskatchewan was probably at around 25 yards. The cover is much less thick and the birds are scattered and not concentrated like they are in my home coverts. I used my shaptail and hun gun bored modified and full with #6’s and did well. I didn’t take shells specifically for the grouse. If I did, I would have probably shot 8’s.
I highly recommend that grouse hunters shoot some patterns at the typical ranges that they shoot their birds. If you hunt in thick coverts you'll see that tight chokes are a real handicap. Compare a cylinder or improved cylinder spread with a modified of full barrel and you'll see what I am talking about. Absolutely no room for error with the tighter chokes and birds messed up with many pellets on the one's you do hit. Go on out there and shoot some patterns and then tell me what you find.
I think some of you guys will join the ranks of Flanigan, Foster. Spiller and Schaldach.
