A better consideration to make when choosing a home defense weapon, no matter what the weapon is ammunition choice.
The are plenty of loadings designed and effective for carbines in home defense situation. A 68gr TAP for one is better suited for that situation than a 55gr FMJ.... the same way 00 or 000 buck would be a better choice over 1 1/2oz slug in the shotgun aztrooper mentions....
In my test medium(24hr soaked phonebooks or newsprint) the Hornady TAP loading saw penetration of just about 11" with great fragmentation. Which is pretty similar to many defensive pistol loadings I have tested in the same medium.
