Good article and I'm glad someone is doing this research. But please pay attention to the situation as posed to the jury:
"The burglar responds with a curse and a threat to kill the homeowner. The burglar does not have a visible weapon. The homeowner then shoots the burglar twice, killing him. After the shooting, the homeowner calls 911 immediately and informs the police of the actions of the burglar described above."
Said situation puts into serious question the need to shoot (see Massad Ayoob's Lethal Force lecture for details on why). The defense does go on to argue that the defendant feared for his/her life, felt that there was disparity of force. But these defenses are weak, and goes to prove that you can't just say things that sound good, they have to be apparently true to other reasonable people. Thus, I submit that the shooting alone -- even had it been with a musket -- would have been likely judged as manslaughter.
I would like to know what the defense attorney said in defense of the AR, if he/she covered any key, relevant facts that other successful defense attorneys have used. The article doesn't mention it.