The Built Bitter set bonus says it improves weapon reload speed based on the number of stacks but as show in the video, even at max stacks there seems to be no increase to reload speed. Tests were done on Void Titan with 120 weapon stat and no reloader mods. Tested the shown Auto rifle and a heavy grenade launcher, in both the shooting range and EDZ patrol. Edit: Upon further testing, it seems that this happens when you load into an activity with the set bonus active. Swapping off and back onto the armour causes it to function as normal.