Red Rose Virus

I'm receiving the same problem with a M1014 shotgun and 12 gauge ammunition. I have 6 slots on my person being occupied by the slugs and yet my weapon reads 0 ammunition available. So reloading with the new ammunition is not an option to me, the menu to switch ammunition types isn't even popping up (suggested that it should once I ran out of 12 gauge pellet ammunition that I was previously using with the weapon when I fist retrieved it).