Solved
Weird bug (PC) gun wont fire but only with controller on first level of campaign
Weird bug, played the game for the first time today, solo campaign, got to the second gun rack just after deleting the plans (spoiler?) picked up the rifle and was suddenly unable to fire, restarted...
From what I recall, in the brief time I tried using a controller, the game was getting confused as to whether I was playing with mouse/keyboard or controller. So, if you're hellbent on using a controller on PC, you might try unplugging the mouse and/or keyboard.
In general, my recommendation is what you might expect - stick with mouse/keyboard if you're playing on PC.
