Trying to envision how good it would be as a club in close quarters fighting...
Bayonet stab!
Butt strike!
Butt smash!
repeat until arms fall off
Smack someone with the butt and it looks like you might bend and jam the magazine in the gun. I don't know if that's worse than the older M-16s which would (I've heard) shatter if you whacked someone with it, but it's something you'd have to think about in close quarters fighting.
They put a bayonet on the thing so you know they thought at least a little bit about how to use it as a combination sword/spear/club, but I do wonder how the magazine and receiver will handle the abuse. Using your rifle as a club a few times shouldn't destroy the gun. IMHO.