Wound Up with that higher and It is chrome bore barrel in the future. I do think it's an A1E1 from some nomenclature I noticed but unsure as I've by no means observed Yet another 1. I figured this was produced across the time of solution advancement on the M16A2 https://selfbizdirectory.com/listings501363/the-basic-principles-of-colt-combat-unit-rail-gun-45