7.5-15% Weak Spot Damage. Weakspot Kills also ignore Enemy Hit Mass.
Continuously chaining more than 2 attacks gives 2-5% Power. Stacks 10 times.
4.5-6% Close Range damage on Repeated Hit. Stacks 5 times.
Gain 7-10% Close Damage for 3.5 seconds after killing an enemy at close range, stacking 5 times.
Gunpsyker with the Columnus is insanely strong right now. You can pop Scrier's Gaze whenever it's off cooldown while not having to worry about blowing up since you mostly will use either the gun or your trusty combat axe.
I pick Brain Rupture over smite because of the passive ability Kinetic Flayer. It's also a decent alternative to take care of far away targets or bosses like the beast.
The rashad is in my opinion still the strongest pick due to its versatility. It's good at horde clear, single target and bosses. Pair that with the finesse benefits from Scrier's Gaze and see how hordes and elites fall down like sacks of potatoes.
The meat of this build is ofcourse your ranged weapon, the Columnus MkV Autogun. Most of the time you will not have to even brace this weapon, just spray away at elites or specials and it will do an amazing job.
I'm picking Warp Siphon over Disrupt Destinity to simply save some brain power. It's also a hassle to always look out for marked targets and on higher difficulties you will constantly run into a plethora of Specials/Elites, which makes stacking your charges pretty easy.
You are a glass cannon now and will have to know how to effectively play in close combat and need general awareness of positioning and enemy placements. It's a high risk high reward build but once you get a feel for it it's probably one of the strongest builds out there.
Happy purging.