Safest kind of 5.56/.223 for home defense/reduce over-penetration?

Only a fool uses a rifle for home protection

You're going to be scared, adrenaline is going to be flowing... very likely it will be dark and you expect to place one round in the bad guy.... good luck.

Get a shotgun.

There are military complaints of very close range combat where 5.56 the bullet passes through the enemy's body and the enemy still functions. In Israel, a couple of guys used a M-16 to commit suicide. Not only did the bullets go through their skulls, but through a foot of brick (the outer wall of the hotel) as well. Interior walls are just 1" of dry wall (counting both sides together) with some wooden framing.

Why on earth would you use a high-velocity rifle cartridge for home defense?

If you really must have a firearm for home defense a handgun is a joke and a high-powered rifle is more likely to injure your friends, family and nieghbors. Get a side-by-side "Coach Gun" type shotgun with the shortest legal barrel available. Absolute simplicity to operate (less to go wrong in the heat of the moment), does not require the skill or precision of a handgun to be effective and won't go through your nieghbors house and his/her nieghbors house like a rifle would.

Don't use such a high velocity round. Use 9mm or .45. If you need a butt stock to sit in your shoulder then look into a rifle chambered for 9mm or just go with an MP5.

Personally, I own a Glock 19 and 1911 for home defense. .223 is going to go through most anything at such a short range (muzzle velocity 2,970 feet/second).

I just hope (for your neighbours that you don´t live in a flat)

Sorry but as said a 5,56 is not for home defence.

btw. a 5,56 hp will make about the same "hole" into a body like a FMJ will do on 5 yards.

(Btw both will fly trough if you don´t hit a bone).

The bullet is WAY to fast to deliver it´s "energy" to a person who does not at least wear a bullet resistant vest.

(In other words the HP won´t expand inside the body because of too less "mass" of the human body at this range)

5.56 travels so fast that frankly even a rubber bullet might go through your walls. Do yourself a favor and buy a pistol or a short shotgun instead.

That'll go straight through your f88king house mate. Stick to a pistol that won't kill everyone in the house across the street.