I like all the work you have put into the possibility of SA Hickey firing the AR-15. I draw the line with your pushing a clean shot from the AR-15 would only "dent" the chrome striping above the JFK Limo Windshield.
It would be good if someone did tests re the dent of an AR15 hollow point (versus non-hollow point) on a chromed stainless (preferably with a bent/crimped shape as per limo) over a strong steel rectangular tube (as per limo).
I used 30 stainless steel droppers/spacers for my balcony fence. I drilled 13 small holes per dropper for 13 stainless steel horizontal wires (390 holes).
I drilled 26 holes in each of 11 heavy channel mild steel columns spaced at intervals along the fence as a part of the fence (& for roof support).
Drilling the small holes in the SS was murder.