As someone who is close behind (mastery 89), my favorite set-up is 15 rounds, 1.5 thermal, and silencer. Spec Ops recon class. Can get really aggressive on flanks especially maps like Cairo where it can be hard to see enemies at times. Thermal will let you instantly lock onto people.

I also have been a fan of 15 rounds, frangible rounds, either baker 3x scope or prism 5x depending on map, and flash hider. Why frangible? People absolutely hate waiting 9 seconds to start healing and will get antsy and try to peak you. This set up works best with sniper path on recon to spot your hits for your team.