In A3 we can only create IR laser and not the visible laser by human eye.
Basically it needs Laser Sights on Weapons.
How do I put laser sights on weapons
Place a memory point called "laser_pos" on your model.
The laser will emit from this position, parallel to the bore (muzzle/chamber) line.
Place the following line in your weapon's config.cpp: lightMode = X;
Replace X with one of the following numbers:
0 no light / laser possible
1 visible to the naked eye
2 visible only with NVGs
3 visible with either NVGs or the naked eye
Toggled via the normal laser toggle command, default is "L".