I am a retired detective that has seen too many autopsies on bodies that were either shot in houses, street corners, and any other place they shouldn't have been when the shot let loose. I won't recommend any load. Just some facts based on thirty plus years on the street. I am not a M. Ayoob or an expert. Just a long time cop that has been there, done that.
There is not much chance of a person surviving a shotgun blast at 10 yards (30 feet) even if the person has heavy clothing on. No matter what shot size you use, at 30 feet, a body hit in the vitals, head, chest, upper abdominal area, that guy is dead or totally incapacitated, usually to die shortly from numerous shot, wadding, clothing fiber, etc. The smaller the shot, the less the chances for the medicos being able to save the bad boy. Even the promo loads that you would normally use for dove and quail are very deadly at 30 feet. If you hit the bad guy in the T-zone, your and his worries are over. Almost no one survives.
If you hit the bad guy in a non-vital with a 12 gauge slug, you may not stop him. Hit him in the T-zone, he is dead and so is everyone behind him for a long way. The only short range shooting that I have observed that didn't kill was an officer that was shot from about 10 feet in the abdomen with 00 buckshot. The shot blew a hole through him but didn't hit a vital organ, took out one kidney. He spent quite a while in the hospital but went back to work after a year or so.
The problem with small shot is that even if it doesnt immediately kill, there are hundreds of penetration wounds where the shot has taken contimanants, such as clothing fibers. If he is hit in the vitals, he will probably be dead from bleed out before the doctors can get to him. If he is hit in the shoulder, or legs, or in the abdominal area, even if it is with a slug or buckshot, he has a good chance of surviving. You have certainly stopped him which was your goal all along.
What do I personally have in my home for protection? A pump with #7 1/2 bird shot. My house is two rooms wide at its widest viewing angle. Less than 30 feet as I must stand somewhere to shoot. My gun has a 24" barrel. I will probably be in the center of the room or at the doorway. Thus it is only 15 feet or less to the other wall. There is no way that a bad guy can survive a shot at that distance unless I wing him. Even a 50 cal won't stop him if he is winged. If I completely miss him, the small shot will expend some of its energy penetrating the drywall on both sides and will still be somewhat dangerous to family or neighbors on the other side of the wall. But, not as dangerous a buckshot or slugs.
Out at the farm, I keep a 30-30 Marlin. I don't use a shotgun for longer range protection. If he comes in the house, my shotgun should take care of the situation. If he is trying to steal my equipment or do my property harm, I will use the 30-30 to terminate his activities.
To each his own theory as to what is best for his own circumstances.
