this was 15+ years ago. I don't believe the M4 existed then, let alone the penetrators. I admit to not having the best memory of the specific nomenclatures and so on. I just recall it was at close range (within 50 meters) and 5.56 ball ammo.
Yes, anything CAN do a through-and-through, even hollowpoints. There is no perfect ammo, and if there's a CQB-battle/hollowpoint round available for the AR15 (I admit I've only recently gotten into the civilian variants of the US Battle Rifle) on the civilian market, I would be just fine with using it in a home defense situation...
...except I still wouldn't, as I wouldn't want the prosecution to be able to hold up an EBR in court if things went that way. I'll never shoot a retreating perp, and again hope never to have to shoot anyone in this context- but knowing how our legal system is, I'd not be surprised to be dragged into court even with a morally "good" shoot.
However, I am now dragging us down an entirely other Rabbit Hole- my apologies.