Zombie Eradication Rifles: Patriot Ordnance Factory

I have been researching automatic rifles (ARs) for zombie eradication work. Patriot Ordnance Factory makes an interesting gas piston variant of the AR-15 that they call the POF-415 and POF-416. AR-15.com has a forum for POF here. A review of the P-415 in 6.8MM begins with this interesting proposition: "For many years now the argument has waged back and forth between 5.56mm and 6.8 SPC. “Which one hits harder, which one is better?” The questions and claims fly back and forth. My two cents on the matter is simply this, I’ve seen some massive wound cavities created with 5.56mm. I’ve personally blown holes through soft-armor clad ballistics dummies using 7.5-inch 5.56mm SBRs. I’ve watched 5.56mm Hornady TAP in 75-grain pierce holes in Level IIIA body armor and blow out sections of ballistics media measuring 5 inches in diameter and another 5 in depth. I know that the heavier rounds in 5.56mm will get the job done quite well. Yet with all this information, I’ll tell you hands down that given the choice to carry a 6.8mm or 5.56mm chambered weapon into the fray, I’d go with 6.8mm any day of the week. Anecdotal evidence proves that the current M855 steel cored rounds that our soldiers are being forced to use are tantamount to spitwads in a fight. Don’t misunderstand me on this, M855 is an excellent anti-material round but it acts like a laser beam on people. It goes right through the enemy creating small holes that don’t incapacitate the subject. A gun chambered in 6.8mm on the other hand acts more like an AK-47 firing the always-lethal 7.62mm." - Abner Miranda, Black Guns Magazine,(2010). Small Arms Review did a torture test comparing a POF-16 rifle with a direct impingement M-4 and they blew out the gas tub on the M-4.