444,
I am not trying to start an arguement. You are offering some incorrect information. For simplicity, I am going to refer to the flash, concussion, etc. as muzzle blast.
Let's examine some of what you posted.
This is a reason why many of the people who go in harms way with a carbine are using suppressors. Not so no one will know the gun was fired, but to tame the blast and noise to a level that will allow them to still function.
To me, this implies that one is unable to function after firing an AR-15 indoors. Not true. You can fire an AR indoors and continue to function fine.
The muzzle blast/concussion/pressure wave..........whatever you want to call it, is significant. You can splint hairs that it isn't exactly like a flash bang: that was just an easy to picture example.
Firing an AR15 inside a building, inside a vehicle, inside whatever is probably very similar to a flash bang grenade going off (I have never experienced a flash bang, so I may be FOS).
Okay, you are FOS. Once again, other than there being a flash of light (which is nothing like the flash produced by a flash-bang) and a loud noise (which is nothing like the loud noise produced by a flash bang), it is nothing like a flash-bang. I am not splitting hairs. A rifle shot generates approximately 120 decibels. A flashbang generates around 170 decibels. I have no idea how bright a rifle's muzzle blast is, but I highly doubt it comes close to the 2.4 million+ candlepower a flashbang puts off.
I think if you review my previous posts, you will see that I acknowledged the muzzle blast is significant. That is based on perhaps hundreds incidents where I fired either an M-4 with military ammunition or an AR-15 with a commercially available loads indoors without the benefit of hearing protection. You on the other hand portray the muzzle blast as debilitating. I am not sure what you base your claims on.
The sound and the pressure wave are so intense that it is like receiving a physical blow.
If the physical blow you describe is a mild slap to the face, sure. But that statement, when taken in context makes it seem as though you are hit in the head with a 2x4. I would call the muzzle blast uncomfortable. Some would call it painful. It is not debilitating.
If you do it anyway, I would probably go with a light bullet designed for varmint hunting: Nosler Ballistic Tip, Horandy V-Max, or something along that line. A bullet desigend to instantly fragment. I have never fired one at a person inside a building so again, I may be FOS but I have shot a variety of animals with them and think this would be the answer to your question. The suggestion of the 45 grain bullet is probably right along this line.
I think Jeff White addressed this issue nicely. I would add that there are law enforcement and military organizations who are just as concerned about excessive muzzle blast, overpenetration and terminal performance as the homeowner. Ammunition manufacturers have been very good about meeting their needs. I would also add that since, by you own admission, you have no idea how it will work on a person, less was probably more in this case.
If you fire a 5.56 carbine indoors, you will lose your hearing immediately.
Not in my experience. I experienced an effect that was more like having water in my ear. It is important to note that the noise is much worse at the other end of the barrel.
This puts you at an immediate disadvantage: one of your senses is now gone.
I have a pretty good idea of the importance of being able to hear in a tactical environment. Unfortunately, no one was interested in how Richard planned to use his rifle. He plans to use it to defend the choke point leading to his saferoom. The ability to hear is probably not going to be as critical as rapidly incapacitating an assailant if things progress to this point.
Any firearm fired indoors is going to have a negative effect on your hearing both long and short term: the carbine will just be worse than most other common defensive firearms.
I am going to assume by common defensive firearms you are talking about hanguns, shotguns and rifles. It is also worth noting than many handgun rounds are going to have a similar effect on his hearing without the attendant increase in ability to end the fight. A shotgun is way worse than an AR and an AR is probably one of the least objectionable of the rifles suitable for defense.
If you only need to fire one shot, it probably won't matter and in the case we are discussing, this is probably the case. But, it is something to be aware of.
Again, you are implying that it will be difficult to get more than one shot off indoors. Again, not true.
I am sure you had the best of intentions when you posted, but your statements are misleading. By your own admission you are drawing comparisons with no experience and recommending equipment based on speculation. When you consider that Richard is relying, at least in part, on the information provided to help protect his family, that is irresponsible.
, this weapon choice will pose a problem. Thus one may choose to have the rifle round as a backup in this very likely event. And one must consider the need for a good bayonet to finish them off after the 100rnd drum is used up 
