Results were unsatisfactory, leading to the gun being bored out to 12 inches (305 mm) and firing a 706-pound-12-ounce (320.6 kg) shell.

Sometime after 1878, "attached gas-checks" were fitted to the bases of the studded shells, reducing wear on the guns and improving their range and accuracy.

Subsequently, "automatic gas-checks" were developed which could rotate shells, allowing the deployment of a new range of studless ammunition.

Thus, any particular gun potentially operated with a mix of studded and studless ammunition.

The gun's primary projectile was 706 lb (320 kg) "Palliser" armour-piercing shot, which were fired with a "battering charge" of 110 lb (50 kg) of "P" (gunpowder) for maximum velocity and hence penetrating power.