I wouldn't be surprised if the manager at factory is a grass, maybe took the bullets out of the gun as well. Tommy only went out of his office for the fight and this was arranged on the spur of the moment yet Changretta says it was all pre arranged and someone sneaked in and took the bullets out.
Office manager then tries to stop Tommy seeing him by saying he can turn him away if he wants.
Probably way off, but Changrettas story doesn't add up and Tommy and Arfur will suss him out.