These are Call of Duty 4 guns, remade with PMG, both campaign and multiplayer guns are included.
All purpose weapons with good range, damage and accuracy, but outclassed by SMGs in CQB, and by LMGs in firepower.
Burst fire in multiplayer makes it one of the most accurate assault rifles. High damage allows for one burst kills at all ranges with stopping power, but for certain players burst fire will generally be worse overall. In campaign the M16A4 can be encountered with and without a grenade launcher, the weapon does more damage than the similar M4 Carbine, and fires faster, but has a higher recoil.
The M4 Carbine is a shorter version of the M16 with full auto fire. A high fire rate compensates for hte low damage, acompanied with low recoil. Found in the campaign with a Tasco red dot sight or an EOTech holographic sight and grenade launcher.