M1A4ME: The point your Dad taught you is something that everyone needs to learn. The grouse were good teachers--if you want to make the first shot--you need to stop shooting before you aim well. You will hit quicker and kill more in the long run if you discipline yourself to not get in a hurry about getting off that first shot. Rather, concentrate on the aim first and shoot only when you know that you are dead-on with the aim/lead. This makes the difference between 1-shot kills and just expending a bunch of ammo, throwing a lot of lead and not hitting anything.
This is true with shotguns, rifles and pistols. And it is true in every situation where you have only a little time to hit your target. Slow down, concentrate your aim and make the first shot count. Better to take the time to hit on the first shot than to miss and then have less time to make the second shot. Hunting is great for teaching how to shoot in high-stress situations.
It taught me the exact lesson your Dad talked to you about; realizing that you have plenty of time to make the first shot without rushing it and making yourself miss. Quail, rabbits verify and confirm what your Dad said.
Also good point about close shots witha shotgun. Blown many a squirrel's and rabbit's head right off. On running rabbit, I wait until he's at least 20 yards away before I even think about pulling the trigger. (I eat the rabbits) So, if there's no thicket nearby, I may let him run 30 yards before I roll him, less shot in him that way, and because there is more spread, better chance to hit him.
I patterned my Browning Auto-5 16 gauge with #1 Buckshot at 30 yards. So I know inside my house, that is one angry swarm of #1 Buckshot that is going to impact the chest (or head) of an intruder. All of the pellets will hit him at that distance. Way more certainly lethal than any handgun--because it penetrates and distrupts a larger area than a .45 ACP. It is simply devastating at close range. And your point about the Turkey hunter who couldn't kill a turkey with 3" 20 GA--well, he can't kill one with a 10 Gauge either. Funny thing about Gobblers is that you do have to hit the head/neck area to kill them! Otherwise, if you hit the body, they may run off and die later.
Have killed deer with Buckshot (12 gauge) and rifled slugs with this Auto-5 16 gauge; so absolutely no doubt about the POI, the spread or the total lethality of this gun at Home Defense ranges.
Still don't comprehend what was said about shotguns being a poor choice for home defense (especially if you remain still and let the intruder come to you). Only conclusion I can draw is that the poster doesn't know much about shotguns and has no experience hunting with shotguns on larger game. I've killed a couple of coyotes with Turkey loads--one #4 lead from 16 gauge and one #5 Hevi-Shot from Benelli 12 Gauge. Hevi-Shot hits like lightning at 45 yards--no matter what you are shooting at--it is absa-freakin'-lutely dead in a fraction of a second. You can almost see its soul blowing out the exit-side!
Let me add something about making that shot.
This has to do with grouse hunting, in the WV mountains where that grouse gets up quick and gets his hind parts behind some trees, over the spoil bank or above the cut (strip mine terms relating to the old abandoned/non-reclaimed strip mines dating back to the 40's and 50's of the previous century).
My dad was talking to me one day and he said, "Have you ever noticed how you can miss that first shot on a grouse, pump the shotgun, get back on him and drop him with the second shot before he gets something between you and him?" I told him that I'd done that several times over the years. The he said, "Well, think about this some. If you've got the time to knock him down with your second shot, why don't you take the time to make sure you get him with that first shot?"
Think about it. Taking the time to make sure it's a good shot is still quicker than missing the first shot and then hitting with the second shot. No matter how big the target is or how fast it's moving.