I am actually working on a laser (plasma) turret for the USA. I was having the same problem for a bit. I will put my code up when I get home from university but pretty much you have to take the paladin secondary weapon, change the damage type and change the Weapon type to a primary weapon.
Hope that helped
<---- Still looking forward to how it will come out, and ZOOP I think as it was mentioned before if you take the Veteran fire image that will work as they are red and could look like lasers.