Anyone in their right mind does not want this threads scenario to play out. Me especially at my age and a bummed up knee, and hearing loss. No sir it would be a living hell on earth.Everybody wants to play operator, until its time to operate; accordingly, I suspect there will be plenty of "Tier I" ARs laying on the ground if the balloon actually ever goes up.
Any AR that 1. is appropriately gassed, 2. has good magazines, 3. has important bits that can work loose staked, and 4. has a quality bolt with spare would likely be plenty reliable. You can pay for those things, or do/test them yourself if halfway competent...most would probably manifest themselves within the first few hundred practice rounds anyway.
Because you practice with your "going to war" rifle....right?