One-hundred and fifty years ago (and one day, as I had other pressing news to report yesterday), Brigadier General Henry Hunt offered a report on the effectiveness of the heavy rifles employed at Fredericksburg the previous week.
I have the honor to report that the practice in the recent battle with the 20-pounder Parrott was in some respects very unsatisfactory, from the imperfection of the projectiles, which, notwithstanding the pains which have been taken to procure reliable ones, are nearly as dangerous to our own troops as to the enemy, if the former are in advance of our lines. In addition, the guns themselves are unsafe. At Antietam two of the twenty-two, and on the 13th instant another, were disabled by the bursting of the gun near the muzzle. The gun is too heavy for field purposes, and can be used with advantage only as batteries of position. For the last purpose it is inferior to the 4½-inch siege-gun, which requires the same number of horses and only half the number of drivers. I therefore respectfully propose that, as the allowance of artillery in this army is small, the 20-pounders be turned in to the Ordnance Department as soon as they can be replaced by light field guns,. and that a portion of the siege train (sixteen guns) be organized to accompany the force in the field for service in such positions as require heavy guns, and, in case of a siege, to form a part of the train. Seven such guns are now here. Twelve were asked for, and it is a misfortune they were not furnished. Two companies of the First Connecticut Artillery are serving with the guns now here. I propose that two other companies of that regiment be detailed, each company be organized as a battery with four guns, the whole to be placed under the command of a field officer of the regiment, and attached to the Reserve Artillery.
Ever since the Peninsula Campaign, the Army of the Potomac included a substantial siege train. Recall the varied set of guns used at Malvern Hill. By December 1862, the Army’s artillery park was more uniform in composition. The field batteries assigned to the infantry formations were by and large 10-pdr Parrotts, 3-inch rifles, and 12-pdr Napoleons – although a few batteries of 12-pdr howitzers remained. The siege batteries used, as alluded to in Hunt’s report, 20-pdr Parrotts and 4.5-inch Ordnance Rifles.
Lending weight to Hunt’s comment about the weight, the 20-pdr Parrott rifle was the heaviest weapon mounted on a field carriage. On its modified 32-pdr howitzer carriage, a 20-pdr Parrott on the march – with limber, ammunition chest, gun, and carriage – weighed 4405 pounds. The caisson with three more chests weighed about an other 4000 pounds.
On the other hand, the 4.5-inch rifle rode on a siege carriage. With limber (no ammunition chest) the 4.5-inch rifle traveled weighing around 7300 pounds. But before you go second guessing Hunt, the 4.5-inch rifle’s ammunition traveled in separate wagons, in loads that were better configured for transport.
The difference here is “field carriage” verses “siege carriage.” The 20-pdr on field carriage arrangement allowed the gun to go into action from the march. The 4.5-inch rifle required more time to prepare for action. But Hunt felt the 20-pdrs “ready for action” configuration was of little value as the gun was too difficult to maneuver into action. On the other hand, the weight of the 4.5-inch rifle was of less consequence as it was employed with more deliberation.
Regardless if you follow that logic, the greater concern with the 20-pdr was, as with all the Parrotts, the tendency to burst. Three failed guns in two actions. That is compared to the near flawless record of 3-inch Ordnance Rifles. The 4.5-inch rifle had not seen extensive service to this point, but would enjoy an air of reliability – at least for the moment. Even later in the war main complaint against the bigger rifle was vent erosion, not bursting.
Despite Hunt’s requests, seven months later the Army of the Potomac still marched with a mix of 20-pdr Parrotts and 4.5-inch Ordnance Rifles. Ironically, given Hunt’s concerns about mobility, it was the 20-pdrs of Taft’s 5th New York Battery on Cemetery Hill on July 3, not the 4.5-inch rifles of the 1st Connecticut. The bigger guns were held back because they took up too much valuable space on the roads to Gettysburg.
(Citation is from OR, Series I, Volume 21, Serial 31, pages 189-90.)