The provisions of this Chapter relating to explosives shall not apply to the transportation of nitroglycerine in capsule form, or in solution, in quantities not exceeding a total of one ounce avoirdupois in weight; nor to the lawful transportation of properly packed ammunition in quantities not exceeding twenty five (25) pounds in weight, nor to the transportation of ammunition by the armed forces of the United States of America or the State of Illinois, or by police officers or other conservators of the peace in the performance of their duties. (1968 Code, §21.307)