Well, the reason I didn't recommend Field Scout is because it's not all that useful if you have Heavy Ammo+ from Raid boots, Heart of the Praxic Fire or The Armamentarium from what I can tell. Isn't the amount of ammo you pick up if tied to your maximum ammo capacity? Thus Field Scout is a must without Heavy Ammo+ and just a magazine capacity upgrade with it. Does Surplus activate in PvP? I don't think so but if it does, then Surplus would indeed be useful. I actually have one with Surplus so I'll test that once I've maxed it out. Surplus is definitely the go to perk for PvE as double ammo is amazing. Either way you'll have to reload once to use all the Heavy ammo from one box and one magazine is enough to drop a whole team of players without reloading. If you want Field Scout, good builds are Smart Drift Control/Rangefinder/Field Scout/Crowd Control (this was sold during the first Iron Banner but with Reactive Reload) and Smooth (or CQB) Ballistics/Rodeo (I've heard you can get this on Legendary HMG but never seen it...)/Field Scout/Crowd Control. I'll try to add these later. Perfect Balance is just nice to have because with AB, which increases the amount of 3HKOs you get by quite a bit, it's not very accurate at all. The Stability is a lot lower than the one you're currently wielding but it does 10% more damage. With Perfect Balance + AB, it does 10% more damage with even higher Stability than what you're using right now and slightly better range, too. You get 60 rounds compared to 36 per crate if you run Field Scout and don't have Heavy Ammo+, though, which is obviously better in that scenario.