NH;
I don't know what's available up there, but your game & fish does. Check their web site. Out here in the Rockies, it's allowed to use shotgun, rifle, or pistol on grouse. The intent is to be able to use a .22 rimfire rifle or pistol as well as the scattergun. I've known people to use a large caliber on them, but it leaves a mighty thin meal afterwards.
A lot of the time, we hunt in pairs. One with a nice 20 guage & the other with an accurate .22 rifle. Some of our species of grouse won't get up unless you pick them up & throw them into the air. No, I'm not kidding.
Keep an eye out for a good BPS on somebody's used rack. With a 26" barrel & the invector choke system. Should run just around $250.00 - 300.00 I'd think. Conditions may vary in your location. An extra barrel, in 28" or 30" for waterfowl & your set. Easy to change and not too hard to find, as a lot of people will trade them into a smith on the shorter barrel in the 20's.
Myself, I've got a 12 guage BPS with a 30" barrel & a 20 guage with a 26". Goofd luck on the finals & hav fun with the guns. 900F