New weapon in Halo 5 beta trailer

I hope im not just blind but if you pause the Halo 5: Guardians beta trailer as the spartans are loading their weapons one weapon I thought was the assalt rifle turns out the counter read 72 bullets in the clip.

I also noticed that when the spartan was running for cover it looked like he was holding the BR but it looked like one but without the scoope.

What do you guys think?

Btw love the new look of the spartans they look bigger and bulkier like a tank idk about the helmet though its kinda meh