The scourge uses two batteries inside of the top end as magazines.
as part of the reload animation those are ejected
however, they are supposed to be hidden inside of the weapon, until the 'flaps' open
on the scourge prime those batteries are rotated by 90° and sticking out the sides
Scourge:
https://imgur.com/a/spurxJf
Scourge Prime:
https://imgur.com/a/NR1wcjE