I prefer the work done by Lex Luthor. He says that AR-15 would have done more damage than merely scratching the cement curb.
The AR15 slug that hit the kerb near Tague had firstly hit the tarmac of Main St, thats why it had lost its thin copper half jacket,
thats why no copper was found in the impact mark (scratch) on the concrete,
thas why they found antimony,
thats why the mark was just a scratch.
This slug was probly shot-1 of at least 4 shots, hollow points.
I doubt that there is a youtube of a hollowpoint AR15 say 55 grain slug ricocheting off concrete, either directly, or, after an initial shallow ricochet.
Have u a source re Luther?