From wikipedia: Robbery is the crime of taking or attempting to take something of value by force or threat of force and/or by putting the victim in fear. At common law, robbery is defined as taking the property of another, with the intent to permanently deprive the person of that property, by means of force or fear.
If the store personal see the gun it can be construed as putting fear in the victim. If it is concealed completely, but your caught "red-handed" at the crime scene the gun would enhancement would apply. But might not be consider robbery if the store personal did not see the gun.
If the store personal see the gun it can be construed as putting fear in the victim. If it is concealed completely, but your caught "red-handed" at the crime scene the gun would enhancement would apply. But might not be consider robbery if the store personal did not see the gun.