No person shall transport, carry or convey, or have transported, carried or conveyed, any dynamite, gunpowder or other like explosives, between any places in Oregon, on any car or other vehicle of any description operated by a common carrier which car or vehicle is carrying passengers for hire. However, it shall be lawful to transport on any such car or vehicle small arms, ammunition in any quantity, such fuses, torpedoes, rockets or other signal devices as may be essential to promote safety in operation, and properly packed and marked samples of explosives for laboratory examination, not exceeding a net weight of one-half pound each and not exceeding 20 samples at one time in a single car or vehicle. Such samples shall not be carried in that part of a car or vehicle which is intended for the transportation of passengers for hire. Nothing in this section shall be construed to prevent the transportation of military or naval forces, with their accompanying munitions of war, on passenger equipment, cars or vehicles.