The Armstrong 7-inch howitzer, also known as the 100-pounder, was the largest ofthe battery of three, placed on raised ground at Hoisey Farm, about 1100 yards to the west of St. Anthony's Hill on which Tower 68 stood. The range from the battery to Tower 71 was 1032 yards.1
The gun itself shows the revolutionary method with which Armstrong manufactured his guns; made of wrought iron instead of the usual cast iron, the gun was constructed by the use of sleeves or bands of iron. The barrel was surrounded by a succession of these bands, each of which was shrunk over the underlying one, with the effect that the metal became thicker in those areas where the barrel had to withstand the greater stress and pressure of firing. This, in turn, had the effect of making the gun lighter than if it had been cast as a single piece, a fact not lost on the Illustrated London News who stated that: "The guns employed were a 40-pounder of 31 cwt, an 80-pounder of 63 cwt, and a short 100-pounder, weighing only 53 cwt....The 100-pounder gun used on this occasion throws shell which weigh 100lb. and contain 3lb. of powder, and yet the weight of the gun with which these tremendous projectiles are discharged is less than that of the ordinary 32-pounder, the weight of which is 56cwt."