I have mostly enjoyed reading this thread. Mostly.
One thing that may have been missed by some is that the OP is talking about an AR-10, not an AR-15.
I have a belt set up for 2 gun or 3 gun range days, and that may be something to consider. A Taco mag holder or two on a belt with your pistol is useful for practice at the range. If you are ever, God forbid, in a situation where your Alamo is about to be overrun, having that handy to toss on may be another solution for you. The bonus to it is that you have practiced with it at the range. Additionally, it can be easily covered with an untucked shirt if you want to just sneak away without looking like a soldier. Finally, in a court of law, you can show that you have it for a specific purpose rather than being painted as someone prepping for a fight well in advance.
A couple of notes about this situation in Colorado, because that is where I live and had to learn the rules.
Lethal force is only authorized in the defense of yourself or a third party when you have reasonable belief that you or that other person is in immediate danger of death or serious bodily injury. It is also authorized if necessary to prevent arson to an occupied structure. It is not authorized to protect property.