I think i found something wrong with the M416. There seem to be two different ARs filed under that name. First of all, let me show you why one of the pics under M416 is not an M416:
As you can see, with the smaller AR, the RIS handle is a bit more round overall and is flat at the end. This is way more similar to the Mk. 18 Mod 1 than the M416. Also, the ejection port seems to be different to the M416's and the same as the Mk.18's. Furthermore, the gun is a fairly short AR. The Mk. 18 Mod 1 is made to be this and is used widely by the Army, while the 10" barrel version of the M416 is not well known (the 12" barrel is used widely though). But, the AR in trailer 2 is in fact the M416:
Note that the second rifle has a longer barrel than the first one. This points toward these rifles being two different ones for sure. The RIS handle of the second one is also quite different and is more akin to the M416. And in the first picture even the stock is the same as the Mk.18's stock. I think that there is a long barrel (more traditional AR) and a short barrel AR in the game. The Mk.18 is a short barrel AR widely used by the Army and the M416 is a long barrel AR widely used by the Army, seems like a perfect fit to me.