When outside in the open I used my sniper rifle, then before going into structures I would switch to my shotgun to collect green ammo upon it's drop knowing I needed to load my shotgun up before I could use it. Like you I was able to work around it, but it was quite a pain and required me to be somewhat sober to remember that. A few times I go running in somewhere and whip out the shotty.... "Click". Oh hey, now I need to punch you since you are so close, Enemy.