The description of this achievement is a bit misleading, at least as of the time of this writing. It leads you to believe that (a) all mod slots have to be filled, and they all have to be level 5 (gold).
The thing is that (a) the vision mods don't even have levels, and (b) they aren't required to be on the weapon at all to count towards the achievement.
Also, the mods you do put on the weapon don't need to be level 5 either - you just have to have something in each slot (vision mod notwithstanding as mentioned above).
I have the level 5 HP5 SMG and didn't have any of the mods at level 5, no vision mod, and the achievement popped for me this morning.