I don't know, but I agree with you that it looks hard to handle. It looks boxy and awkward and not at all like an improvement over what we have now.
Why not outfit our guys with Kalashnikovs? I know that would be a heresy, but those things seem indestructable and foolproof.
I would have no problem with that if they are reliable and effective in combat and there is adequate quality control.
Because even the really nice ones (e.g. Valmets) are piss poor combat weapons in a lot of ways for a highly trained combat grunt. They may be adequate for peasants or poorly trained troops, but their shortcomings are legion if you are little more high-speed and the Kalashnikov system starts to hinder battlefield performance. The M16 may be a poor choice for poorly trained troops, but it is a wonderful platform for highly-trained soldiers.
If you've done urban or CQB with AK actions, one thing you notice right away is that those weapons are slow to operate in a dozen different ways compared to an M16 action. If nothing else, Stoner was detail oriented on the ergonomics side of things. When going up against other well-trained troops operational speed matters, and it can be the difference between your ass and the other guy's.
Ever fire one? Try it and you'll know why.