A first for me also. There is not enough room for the round to flip 180. I believe it would have to start in the mag that way.
Is there a picture of the empty cartridge outside of the firearm?
Is that a live round? If so, the jam is due to operator error.
Most malfunctions in ARs are caused by three things.#1 Bad ammo, #2 bad mags and #3 operator error. #3 is most often a contributing factor to error #1 and #2.
You need a brass punch and a hammer. Place the tip of the punch at the front of the bolt carrier and knock it to the rear.
If you need help, bring it to me.
My theory is its a fired casing that somehow never ejected, or possibly bounced back in (hes a lefty), and got stuck on top of the BCG. Which is odd that a BCG would have a loose enough tolerance to allow a casing to get stuck on top of it. He was just firing at a normal/slow pace and is by no means a beginner.
Yup. Not a common malfunction but learned how to clear it at a WARFIGHTER class. Easy. Stick your fingers up mag well and press the face of the bolt back. While keeping pressure upward chop the charging handle until it seats then pull the charging handle back. The bolt will function as it should and the bcg will move back. The round should fall loose. If not, finger **** it and tickle it. It will fall out.
A first for me also. There is not enough room for the round to flip 180. I believe it would have to start in the mag that way.