In a house though all rifle cartridges a serious over penetration hazards.
Shotgun is the answer for defending the house.
One word. False.
The 5.56/.223 using defensive ammo penetrates much less than 12 ga 00 buck.
That has been proven over and over again, and yet people still see the word "rifle" and assume the round will go through 3 walls, a TV set, destroy the chicken in the fridge, bust out the front door, and kill neighbor Susie while she takes a shower...
I prefer using my 5.56 for defense for the precise reason that it will penetrate less than both
JHP pistol rounds and 00 buckshot...
WTH? Really? Any reported stopping issues with the .223 and pretty much any other cartridge man has devised has to do with the crappy ass solid and FMJ bullets. Clear back in the day of the .45colt everyone but the military figured out that solid pointy bullets zip right thru things doing very little damage along the way as compared to alternative bullets. .223 with good bullets = good, .223 with crappy bullets equals crappy. FMJ = crappy. Who'd a thunk it?
Let me tackle this one too. While FMJ is not my first choice, 55gr M193 ball ammo is not a bad choice if it is all that you have. The FMJ ammo that has a tendency to make a straight line through a combatant is the 62 gr M855 round. The lighter 55 gr has a tendency to yaw and fragment fairly quickly after encountering a barrier or flesh.