That's a great set. Zen Moment is basically the only useful perk you can get in the first slot other than Luck in the Chamber which has poor odds and Firefly is one of the better perks in the 3rd slot. Red Dot OAS has high Stability and with Fitted Stock, you basically won't need to compensate for recoil at all. Explosive Rounds aren't bad and add some camera shake and flinch in PvP and AoE damage in PvE. I rolled one of mine for a similar set with Firefly but I got Final Round instead of Zen Moment.