Evolution I - Incarnon form - 12 headshots (less with multishot) lets you switch to Incarnon mode after alt-fire which has about 408 rounds
Evolution II - Void's Guidance - +50% Accuracy and -50% Recoil. The combination of this perk with Primary Deadhead gives -100% recoil. If you run stabilizer in exilus as well as primary deadhead, you can run Rapid Wrath (+20% fire rate) instead.
Evolution III - Ready Retaliation - +100% reload speed for 6s when reload from empty. This actually also affects the transformation time, cutting it down from 3.4s to approx 1.7s if you manage to reload from empty.
Evolution IV - Elemental Excess - +20% status chance, -10% critical chance. This drops the final crit chance to 10% to synergize with Devouring Attrition and makes the final status chance approximately 70%.
Evolution V - Devouring Attrition - 50% chance to deal 2000% damage on non-critical hits. This 2000% multiplier is currently a separate multiplier to base damage mods such as [Serration], deadhead, [Galvanized Aptitude]