Original build and concept by Pro Secco _ ECM poky sniper with good pinpoint and speed: dual gauss are very high mounted and can be used for safe pokes, 1xERPPC for additional ammo-free damage and/or alpha strike. Full alpha strike can be sustained a couple of times, so don't worry if you screw up timing a couple of times. ECM will greatly help to achieve free trades and will also protect you from getting heavily focused, so XL engine is not a great deal thanks to that. Still, you are fragile due to torso mounted gausses: spread damage as much as you can and avoid receiving damage during cooldowns at all costs +10% energy range and +5% ballistic range to further enhance this sniper / poke role. Recommended skill tree: max range, max cooldown, max ammo, max armor, get a bit of acceleration / deceleration for faster pokes / trades, max ECM, max seismic sensors (optional, but worth it in pugs for those forced close range maps), advanced zoom, UAV or airstrike Spoiler: Skill tree image
UPDATE: IS gauss ammo now has 12 shots per ton pre-skills, so 5 ton of ammo are worth 70 shots post-max skills. Updated skill tree and build. This build is a very nasty sniper in the right hands, don't underestimate it.