Watch The Armstrong 100 Ton Gun (2013) : Full Movie Online Free The Armstrong 100 Ton Gun was first created in the late 1870's, and was easily the largest weapon of the time. Weighing in at 103,888 kg, the 100 Ton Gun had an length of 9.953 meters, and took a crew of 35 men, including 18 men just to handle the ammunition. The gun was originally offered to the Royal Navy, who deemed it too heavy for use. The Italian Regia Marina then took the gun into service.