Ive had this theory for a while but I believe I just confirmed it. The theory is that until you gain all the proficiencies for a new weapon your accuracy is poor and ADS snap barely works.
I just unlocked and maxed proficiency with the Strata yesterday. Over the course of using it I noticed that I could not target very far using ADS until I had gained all the proficiencies. I tested this in the boat room by shooting at the other team by the outdoor stairs using the boat as cover. Before I finished the proficiency I could not target them but as soon as I finished all the proficiencies I could easily target from this position. Hip fire also seems much harder until you're maxed too.
If you don't believe me try this. First play a match using the Stauger with laser using an account with full Stauger proficiencies. Next play a match under a brand new account using the preset "Close Quarters" loadout which has a Stauger with laser. You should notice a huge difference.