I read the book "No easy day" and if I remember right it was an HK 416 or whatever they call it and Black Hills MK 262 ammo (77 gr SMK). It was at the end of a hallway but I don't recall how close. But that's according to the book and my memory, take it for what it's worth.

I do remember the Gen 4 night vision at $65,000 per pair.