For some weapons, you can press "T" to toggle the weapon into an alternate firing mode. For example: the Blaze95 can be toggled to shoot both barrels at the same time.
This is a great feature, however, pressing the "T" button does not always work, and currently you have no way of knowing whether or not you actually toggled the weapon correctly until you fire it. This is similar to how "vaulting" doesn't work all the time.
Idea 1:
Add a "click" sound that is audible when the firing mode changes. (Not when "T" is pressed, but when the actual firing mode of the weapon changes.)
Idea 2:
Add text that indicates the current firing mode to the existing Hub area that displays the range set on the weapon (50m, 100m, 200m ...etc. on upper righthand corner of the screen).