All I know is that if I was handed a "cold" gun for a scene that I'd be performing in, I would say to the armorer "are you 110% certain that this gun is cold?" After he/she confirms that it's cold, I would then take the gun outside and fire it into the ground, just to make double sure. If the gun shoots a bullet, I'd know the armorer is an unreliable, unprofessional fool. If the gun shoots a blank, I'd know it's safe and cool and there'd be no harm done.