That's a significantly tricked out Rhodesian chest rig, I ran one of that style for work for a long time and they're excellent when wearing body armor that doesn't have the MOLLE looping or if there's times you just don't want to run armor at all. I'm not sure why he isn't using both shoulder straps, that's not very stable, but it might be with all the tricking of pockets everywhere on it there is just too much shit on it and it's getting in the way, I definitely like my shoulder straps slick so they don't interfere with my ruck straps. For shooting with straps like that, you square the rifle's buttstock up more in the center of the chest, basically on the inner portion of the pec, head and all are still square.
As for the rest of it, I don't need to spend half an hour on a video to know Cali gun laws are stupid, but I'm glad there's some fine innovators out there to show the lawmakers that no matter what silly rules and restrictions they try to come up with, there's always a work-around. Kudos to them, but glad I won't need to be a customer.
