Does anyone else have this problem??

I posted this in the general discussion thinking it may not be a bug, I didn't get much response so I assume I've done nothing wrong. So here I go.

I am using the Ratslayer and changed ammo from standard 5.56mm to armor piercing, but it then wont let me change back to standard bullets. When I click equip nothing happens, I drop the armor rounds and leave the standard on me but it says my gun is empty. It was doing it yesterday so I left it over night and thought it might resolve its self but no luck. has this happened to anyone else or can anyone suggest a fix??