Technically, it could be done. Someone did the math from the scene in the movie Predator. He could carry a weapon that heavy, including the ammo and batteries. It would be about 40kg for the gun and 25kg for the ammo. That's very high, but not absurd, as long as he's carrying almost nothing else. It could fire for 45s without running dry. And if you limited it to reasonable bursts of say 3s, that ammo would last a while.

It's not practical, but it's possible.