no they’re not, HK91/93/MP5 etc are recoil operated. the roller acts as a delayed blow back system. the HK416 is a piston driven version of the M4 upper. the M4 upper uses direct gas impingement onto the bolt carrier
he HK-91 uses gas to release the casing from the chamber. Technically, it uses both recoil and gas as a function, which is why it is so reliable. Several here misunderstood my meaning , more my fault that anything. But the HK416 is purely a new form of gas operated weaponry.