I hunted a lot of grouse in my younger days. I started out with a russian single shot 12 ga, then a mossberg 500, then a 870 wingmaster. All worked well.
Today I use a sxs and it's mostly because it fits me better. I can't make a 500 or 870 fit me as well as this sxs. I'd need a custom stock and when I consider the cost of that I figure I might as well put that into a faster shooting gun. Nothing is as fast as a double!
My only gripe now about my sxs is that I wish it was lighter weight and 20 ga!
It is very easy to change the fit on a pump gun with a stock bolt.
Buy one of the shotgun laser boresighters, less than 20 bucks on the Internet.
Install it and mount your gun repeatedly with your eyes closed. Then mount and open your eyes. If the bead and laser dot are one you are good to go.
Likely they are not...
Loosen the stock bolt and insert a small piece of credit card stock between the stock and receiver. If the bead is left of the laser dot the shim should go in the left side. If the bead is too low the shim should go on top. You can stack two shims but I try to avoid going higher than that on the first go around.
Take the gun out and shoot it a bit with clayigeons or a patterning board or butcher paper/cardboard to verify what you did with the light.
When satisfied, carefully disassemble making note of shim location(s). Wax the receiver and stock bolt, plug holes in the receiver with clay and make a small donut around the stock bolt hole and install the shims with epoxy.
Cure, then remove the clay before shooting.