When You put a loaded handgun (I have not tested for rifles) in your inventory, and then equip it from your inventory, tou are not able to shoot the gun.
There is no weapon/ammo information on the top right display.
You have to drop your magazine on the ground and put it back in the gun to be able to use it.
Edit: fixed in Beta
Take at least a handgun with mags, and a tactical vest or backpack.
equip the gun, load it with a magazine.
Put it back in your inventory.
Equip the gun from inventory.
Try to shoot.
Edit: fixed in Beta
Mass closing ancient tickets with no activity for > 12 months; assume fixed or too trivial.
If this issue is still relevant in current dev build, please re-post.