Holding down the mouse button and holding shift, should activate power mode, but in my case it isn't. Dunno if it's only me. Watching kill cams, ppl have it activated. On top of that it works just fine in single player campain. Is there any way to make it working in multiplayer?

There is no power mode unfortunately, its a passive mode that is always on and you cannot activate it.

yes u can activate it but only for 1 thing,when aiming down the sights if u press sprint key(my key is shift) recoil will be almost be zero

Same issue here. Activating the power mode in singleplayer works just fine, but in multiplayer it doesn't trigger at all. Every second killcam confims that it's working for everybody else.

There is no power mode unfortunately, its a passive mode that is always on and you cannot activate it.

I think the "power mode" its the maximum armor.