I don't know if there's much you can do about it, but when you get more ammo the ammo display doesn't update until you fire or change weapons. There was also one time when the ammo in use went to -1 for some reason, and when you run out of ammo, the ammo display shows a negative number of remaining rounds. Also, the ammo display on the slam shotgun seems a little borked, it shows up only when it feels like it.
Also, the spinning ammo idea isn't exactly all that good.
If I were you, I'd have some ammo standing up straight, for good looks in some builds, or down, to give it a little bit more realism.
and that LR rifle is okay, but for it to reload like a shotgun would be nice.