It's to be very powerful, but it is not a belt-fed monster, it cannot be ironsighted, it cannot be fired/deployed whilst running (only walking), due to its firing method it is not reliable for longer ranges at all, and its fire rate which is slower than the AK will make it so that while it's really powerful and rips into the small zeds as a commando would, it cannot hope to take on the big zeds due to not being able to fire fast enough before its user is killed, and the mando may not be able to carry another assault rifle with it, and will have to settle with a Handcannon or smaller.
That's the basic idea pulled out of my old thread anyway.
Just to clarify, when holding the weapon, the player can run, but not shoot. Upon pressing the ironsight key, the weapon is "deployed" in a hipshooting position like the one shown in the video, and the player can move and shoot-n-move in walking speed only. It has 40 rounds base, 50 rounds on lv6. The low fire rate makes these magazines last much longer. There's a sizable number of spare magazines, but not loads like with the assault rifles.
It is also to be quite stable when firing, but its recoil is mostly made of side-to-side juddering which makes it so that while sustained fire in shorter ranges is plenty doable, it's virtually impossible in long ranges so the Bren user has no hopes of doing stuff such as kiting or whittling down the zed's health before it can reach him.
So it keeps the commando within its usual crowd control role.