72-round weapon in H5G??

I noticed before a curious weapon in the E3 multiplayer beta trailer. Now, I see it is just a battle rifle without its sight. But there is still something that intrigues me. What is the 72-round rifle? Was it a place holder for something? Is it a deleted weapon?

Halo 5: Guardians - E3 Beta Trailer - YouTube in the IGN trailer for the beta, around the 10 seconds mark.

We thought it was the MA5K carbine at the time. But now it seems it was just a flawed or preliminary BR model. Still, it is a little odd to have 72 on the counter in the first place. Maybe it’ll be a variant?

Having the MA5K in game would be truly awesome, but it could be as you said, it could be a preliminary model. And the lack of a sight in the BR supports this.

Hope so bruh