Someone may have already touched on this, but you are correct. The 416 uses the same exact lower receiver, stock assembly, and magazine as the M-16/M-4.
The only thing that gets changed out is the upper reciever assembly which will be the same thing that happens IF and when the Army goes with the 6.8mm round. That is a big if since we would have to get NATO on board to do that because the current 5.56mm is the NATO standard for rifles.
I was in the AF when they were the first to procure the AR15. As it evolved into the M-16 and caused so many problems in the Army, I have always mistrusted the system, even though it demonstrably improved.
Guess I also never quite understood the .223 as a military round. My prejudice was that it was a varmint round ... wouldn't dream of it on deer! Plenty lethal at close range, I never though it could do the job down range, or against a skinned vehicle, for example.
As a kid, I hunted everything in Maine with a 6.5X55 surplus Swedish Mauser, which I still have and still use occasionally with commercial sporting ammo. Just the handiest damn weapon, excellent at long range and extremely accurate, deadly even on a moose! So when the Army announced the 6.8, I thought "Hey that's more like it!"
I have two youngsters ... a niece and a nephew ... in Iraq and Afghanistan. I want them to have the most powerful reliable weapons they can handle ... even if I have to buy them.
I just finished reading the book Black Hawk Down (I know - I’m about a decade late on that). I was amazed to read about how much our troops hated the 5.56 ammo. There were several instances in that battle where they had to shoot someone 10-15 times to kill them.