On September 24, 1863, Major John Barnwell of the Confederate Ordnance Department conducted a routine inspection of batteries on James Island. The next day he filed his inspection report. The first half of that report was routine and related details of which guns were in what battery, the state of the guns, and the ills of ammunition storage. But in the second part, Barnwell offered remarks about the ordnance, projectiles, carriages, and mortar beds. “The conclusions arrived at are based on the evidence of facts and experience in the field, and will be placed before you as concisely as a clear expression will admin.”
To start with Barnwell brought up the the grove pattern used on rifled guns. Specifically the shape of the groove:
Some manufacturers of ordnance deny the fact that a gun is weakened by rifling, and attribute their frequent bursting to the heavier projectiles used. While there is some truth as regards weight of projectiles, it is a fact that the fractures in rifled guns follow the edge of the groove exactly as ice and granite fracture in lines cut upon the surface. It is known that acute re-entering angles upon the surface of guns are the usual lines of rupture, hence the present external form of guns without moldings. From these facts, no rifled guns should have acute or sharp-edged grooves, but a flattened curve thus /¯¯¯¯¯¯\ as a Parrott, which, though it does not remedy the injury from rifling, has been proved to be the least injurious form.
I’ve never heard, from wartime accounts, of a cracking pattern as alluded to above. Interesting that Barnwell cites Parrott rifling as better for endurance, without naming Brooke or Blakely.
Next, Barnwell took on the nature of reenforcing bands on the guns:
Banded guns, facts and experience prove, to be weaker at the breech than at the re-enforce, as of four which I have examined on the front of our defenses, all have fractured square at the vent, throwing the breech to the rear. If the breech is strengthened, explosions would not be so frequent.
Barnwell mentioned the Brooke strap system, like used on the triple-banded guns. But most preferable, according to Barnwell, would be a wrought-iron case that covered the entire breech area (which some Blakely guns were using).
Barnwell then offered his observations about rifled projectiles:
We are certainly in error as regards weight of elongated projectiles, which requires immediate correction for effective service, as well as on the score of economy. We must have some safe, fixed limit determined for the weight of shot, beyond which weight it should be made penal to serve, for we cannot afford experiments in the field, excepting at the cost of dismantling our works, and this it would be more judicious, as well as economical, to leave to the prowess of the enemy.
He offered an example to illustrate his point:
In Battery Haskell we have 60-pound shells and 80-pound shots for 24-pounder rifled guns. The initial velocity of 1,600 feet per second has been fixed upon by the experience of the past as a maximum for economy and efficiency for a 24-pounder and some other calibers. To double this velocity, if possible, would be straining the gun beyond a safe limit, yet it is a common practice here to use projectiles of twice the weight, which is equivalent to velocity x 2. To meet this additional strain, guns are banded, and the economy of the service demands that the banding should increase the strength of the piece to twice the resistance of the casting.
Barnwell observed that rifled guns firing very heavy projectiles were unsafe after 300 rounds. By comparison the smoothbore guns were able to safely fire 1,500 rounds. He recommended the ordnance department restrict the projectile weight to double that of the caliber.
He then turned to the subject of carriages.
Experience as regards columbiad barbette carriages shows that they are too weak in design and plan to sustain long-continued firings at high angles. In one of our batteries out of five pieces all are without eccentric wheels. It is respectfully suggested that the use of rear eccentric wheels be abandoned; that strong lunettes be placed on the rear and bottom of the carriage, to be worked with rolling handspikes.
The Federals on Morris Island used, for the most part, wrought iron carriages. But Colonel Edward Serrell’s carriages on Black Island were strengthened for firing at elevation.
Lastly Barnwell mentioned the mortar beds, saying “wooden transoms will not answer. There are four mortars in our batteries which are unserviceable from this cause.” Major Thomas Brooks, on the Federal side, had already encountered this problem and resolved it with an improvement over regulation mortar beds.
Barnwell’s recommendations went to Colonel Gabriel Raines at Augusta Arsenal. But at this point in the war, there was little the Confederates could do to modify weapons construction techniques. However, projectile technology was still evolving. This was direct feedback on new technology, in 3 out of 5 cases, from the field.
(Barnwell’s report is from OR, Series I, Volume 28, Part II, Serial 47, pages 378-9.)