From the last weeks of June 1863 right up to the fall of Charleston in February 1865, the story of the siege was dominated by the sound of heavy Parrott rifles firing bolts and shells towards the Confederates. The performance of these heavy rifles was extreme for its day, and duly noted by observers. Just as noteworthy, however, was the rate at which those guns failed… sometimes dramatically failed. As some went looking for explanations, bad light reflected upon the weapon’s inventor – Robert P. Parrott. On June 21, 1864, Parrott sent a letter to the Commander of the Department of the South, Major-General John Foster, offering his analysis of the problem and a solution… and a novel suggestion to use the big rifled guns in yet another manner:
Office West Point Foundry,
30 Broadway, New York, June 21, 1864.
Maj. Gen. J. G. Foster-
My Dear Sir: Though I suppose most of the points of importance in regard to the service of my guns are by this time understood, there are one or two that are of such exceeding interest that I am induced to mention them. The greatest difficulty now to be encountered is in the premature explosion of shells in the bore of the gun. The charge of powder they will hold is quite large, and owing to the elongated form of the projectile or to its being driven into the groves, there seems to be a tendency of the parts of the broken shell to wedge in the bore, thus carrying away muzzle or some other part, or, at any rate, giving the gun a violent strain which is afterward and perhaps by other accidents developed into the destruction of the gun. As a means of diminishing this danger, I am now lacquering or varnishing the interior surface of the shells. Even when freshly put in it operates favorably. A little poured in at the fuse hole and then caused to run over the sides by laying the shells down and rolling it will answer.
The reason for this seems to be that on firing the gun the powder charge of the shells is violently thrown back, and explosion is caused by the friction or attrition of the powder against the rough surface of the bottom and sides of the shell. These are made smooth by the lacquer or varnish, &c.
I have used the 100-pounders as mortars by loading them with a very small charge of powder, 3 ¼ pounds, and setting out the ring of the projectile in one place only so as to nearly fit a groove, by this means, which admits of the shell going down, merely placing the expanded portion in one of the grooves of the gun, and have got a high-curve traveling, say a range of 2,000 yards, with 20 degrees elevation. I have no doubt that when such a fire happens to be desirable it can be obtained readily with the heavy rifles. The starting out of the ring in this way causes it to take the grooves with this low charge.
With the best wishes for your health and success, most truly, yours,
R. P. Parrott.
What Parrott described here, and in other correspondence, was the “rasping” of the shell powder within the shell itself when movement initiated on firing. More so than in a standard smoothbore shell, the rifled shell was moving violently on two different plains of action. This friction, he felt, caused the powder to ignite prematurely.
Throughout the long months of use on Morris Island, gunners greased, flushed, and cleaned their Parrott ordnance. Though I’ve often noted in those wartime photographs, the shells seemed haphazardly lain in the beach sand. Now, with Parrott’s advice, the ordnance crews preparing the shells had an additional precaution of lacquering the interior.
While a sound, logical step to take, nothing could repair the damaged reputation of the guns…. And at the same time, the faith of the ordnance department remained, for the most part, unshaken by the bursting guns. West Point Foundry continued with deliveries of large caliber Parrotts. And the Army kept using them – for decades to come.
And since I’m discussing Parrott and West Point Foundry, let me mention again a portion of that cannon production site is set aside in a park along the Hudson River. Furthermore, Trudie A. Grace and Mark Forlow’s book on the history of West Point Foundry is in bookstores and available on line now.
(Citation from OR, Series I, Volume 35, Part II, Serial 66, pages 143-4.)