M4A1 Carbine vs M16A2 Assault Rifle game mechanics

[Mahatatain]

I had an interesting query from one of my players last night - his character is armed with a M4A1 carbine and he pointed out that (apart from the higher ROF) it seems to be a much poorer weapon than an M16A2. Now he's focussing on the Range increment and the way the game mechanics works with range but his point was that if the American forces have seen fit to convert most of their units from the M16 platform to the M4 platform then that seems to be contrary to what most roleplayers would do and is therefore a challenge to the rules.

Does he have a point here? Is the range increment for the various M4 Carbines too low and it should be much closer to the M16's range increment?

Opinions please.

Thanks.