After unlocking and applying the hologram on your Scar in the settings page, how does one activate this gadget on your rifle after in game? Can you use it in the MP demo?

press 2 to change the "fire type" on your gun. it should change to a very small aiming reticule, click once to fire your hologram then remember to press 2 again to change back to normal firing mode

Also, if you're playing on xbox, it's left D-Pad to switch to hologram, and left D-Pad to switch back to firing mode.

They really really need to modify this so that when you deploy it reverts back to rifle fire automatically!