The HK433 is a modular assault rifle chambered in the common 5.56x45.
It is made in germany by the famous HK which are also the producers of the MP5, MP7 and many more.
It was designed to be appealing to both users of the G36 and HK416, essentially combining it into one rifle.
LShift (Left Shift): Fire
P: Change fire mode (From semi-auto to full-auto and vice versa)
H: Aim (stabilize, good for negating muzzle rise and if a human is holding it)
To put it into someones hand, disable the collision on the humans arms, put a phaselink from the main part of the stock to the human and put it in its hands.