Craig, I would trust Frank's judgement on choking a bird gun without question. I did the same thing you're considering about a year and a half ago. I have a sweet Fox 20 Sterly Ejector that I wanted to be my dedicated quail and woodcock gun. Dean Harris opened it to .006" and .016", at my request. Used it last season on several hunts and found it to be perfect for my needs. He also lengthened the chambers to 2 3/4" for me while he had it. I have been pleasantly surprised at how hard the .016" barrel hit some wild flushing, rather long quail.

I know quail and woodcock won't be the primary game for yours, and I freely admit to knowing less than nothing about grouse. If I were to be "building" a grouse gun I would feel perfectly suited to follow Frank's lead.

Grouse gun chokes are interesting topic for me also. Much depends on how and when you hunt them. My choice being hunting with pointing dogs, and young ones almost exclusively, I don’t shoot wild flushes. No matter how much experience a dog has with grouse some birds are going to get bumped, but when all goes well the experience is up close and personal. With both grouse and woodcock I would be confident in saying inside 25 yards for the open first barrel. And although being sick with “ the next ones the best one”. The gun that’s first out and most successful is a 20 ga with .005/ .010 with 7/8 oz of 8s in the right and 7 1/2 or 7s in the left.

I also have a very fine and great handling flushing dog that I could brag on his large number brought to hand birds. For his work I require a bit tighter chokes, even though I can read him well and know when he’s hot. The distance to first shot is frequently a bit longer.

I would suggest you borrow an open choked gun and shoot it some at clays to get a feel for what it will do. A Q1/Q2 repro would fit the bill quite nicely. You just might be pleasantly surprised. Make sure you use the ammo you intend to hunt with as the shell alone can make a huge difference in pattern performance. When it comes to woodcock and grouse it depends what dog you are hunting behind. It does not matter much what choke you have at 10-15 yards. Even a cylinder bore will blow a bird to bits if centered.