Things fun. Slow and not good enough, but i got a riven and figured id give it a shot and good

Cascadia flare is the best option, [Galvanized Crosshairs] can be swapped for [Primed Pistol Gambit] or [Creeping Bullseye], [Accelerated Isotope] and [Lethal Torrent] are interchangeable ish, and you can swap [Primed Quickdraw] with anything you want, probably [Lethal Torrent] or expel. [Primed Convulsion] seems undervalued by the math, but also removes heat, therefore breaking cascadia flare, which is also the most important part of the build.

I don't personally want to put [Steady Hands] on the build, and have used it, with crazy fire rate, without wanting it. Actually haven't put an adapter on it, but if you do, id say [Lethal Momentum] to help your accuracy and hit heads for crosshairs more often.

[Magnum Force] doesn't belong in any build, unless you're building for inaccuracy specifically.