I use the Bearpaw rubber blunts. They tend to slow down a bit more when hitting a grouse with a bow setup for elk, and they don't tend to knife under vegetation. Most of the time they are just laying out on top of the ground somewhere behind the bird. They make a heck of a whop! sound when you thump a bird with them, you know when you make solid contact with one.
I have also just used a field point with an Adder Point behind it. They just pinch between the field point and insert. They are okay, but I prefer the blunt tips.
Absolutely make sure you do a good visual inspection and flex check arrows after thumping a grouse with them.