General Gillmore reported in his after-action assessment of the siege by his artillery, "Good rifled guns, properly served can breach rapidly" at 1600–2000 yards when they are followed by heavy round shot to knock down loosened masonry. The 84-pounder James is unexcelled in breaching, but its grooves must be kept clean. The 13-inch mortars had little effect. The new 30-pounder Parrott Rifle had made a major impact on the battle. The rifled cannon fired significantly further with more accuracy and greater destructive impact than the smoothbores then in use. Its application achieved tactical surprise unanticipated by senior commanders of either side.