Good to hear! And indeed, I never realized that you need to 'pump' the shotgun, good to add as a hint indeed.
My playing style is that I want to use other keys as less as possible. So one hand on the mouse, other hand on the WASD keys, so anything I use frequently I would like to be either within easy reach of my keyboard-hand or with the mouse, without having to look. Q and E could have that effect, 1 - 5 are a bit harder. I know, I am spoiled ;-)
Keep up the good work!
Edit: Btw, using the pumping with right mouse button feels really good, really gives that Boom-click-clack feeling ;-) So indeed, don't change it, but add a hint.