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tube and be sufficiently strong to leave a wide margin of strength with the then service charges. From the same reasoning, as from actual experiment, it will be seen that the heaviest battering charges can al80 be used.
In England, as early as 1855, a great many devices were proposed and many of them tested, to strengthen the cast iron ordnance of the day to meet the increased strain to which gups were subjected by the use of heavy elongated projectiles. Among others were shrinking onto the breech of the gun wrought iron bands and wrought iron jackets (our Parrott system), putting on a bronze jacket, and lining with steel tubes of various qualities, but without any decided success, and it was not until 1863 that the Palliser system of living a cast iron gun, previously bored out to a size greater than the original caliber, was proposed, and experiments were made with it. These experiments extended over several years and the results were so satisfactory that it was recommended by the Ordnance Select Committee of 1868 to make extensive conversions of smooth bore guns on this principle, "in order," to quote the words of the report, “to provide at a cheap rate rifled ordnance for secondary purposes of defence.” This recommendation was carried out so far that there are now in service over two thousand of these converted guns, which are, as a general thing, distributed among the smaller vessels of the navy, and mounted in sea-coast fortificatious where there is a limited range. Sir William Palliser claims that not a single gun converted on his system has ever failed or burst in service; and in exhaustive proof firing where extreme efforts were made to burst the guns it took most extraordinary measures to accomplish it, as will be seen by a few examples given below, which are taken from the report of the Ordnance Select Committee.
1. A 6.5 inch gun burst at the eighty-first round of a proof series with 16 lb. charges and cylinders increasing by the weight of op shot every tenth round. The weight of the cylinder used when the gun burst was 599 lbs, length 74 inches, length of cartridge about 16 inches, while the total length of bore was 123.75 inches.
2. A 6.3 inch, gun couverted from a 32 pdr, burst after 111 rounds of a proof series, with cylinders from 50 to 150 lbs., while firing a 150 Ib. cylinder and 30 lbs. of powder, splitting externally but not going to pieces. Five shells containing 41 lb. bursting charges had been intentionally burst in the bore, but notwithstanding this the gun was subsequently loaded with ease.
3. Another gun of eight inches caliber converted from a 10 inch S. B. was fired with extreme charges and 180 lb. shell, with ten to fifty inches air spaces, and four shell with 123 lb. bursting charges were intentionally burst in the bore. This gun is still good.
4. Another extraordinary example is that of a Xinch cast iron gunconverted into an 8 inch rifle and weighing but four and one-half tons, proved as is the 8 inch Woolwich gun of pine tons with two charges of 39 } lbs. R. L. G. powder and shell of 180 lbs. This gun as a smooth bore had gone through the siege of Sebastopol, had been struck by Russian shot, and the vent had become so enlarged as to admit a man's finger. After the two regular proof rounds this gun was loaded with a charge of 22 lbs. of powder and a shell of 120 lbs. containing a 12 lbs. bursting charge. This shell was put into the bore with its point towards the charge, the fuze hole left open, and rammed home. Five rounds were thus fired, bursting the shell each time, but even after tbat, and although the bore was necessarily somewhat scored up, the gun was easily loaded. After this the gun was fired several times with fifty inch air spaces purposely left between the powder charge and projectile, but I do not attach much importance to this test of a gun's strength, as it has long been known in this country, where, after the war, a Parrott gun was subjected to extreme tests, that such air spaces diminish the pressure on the walls of the gun*
Many more examples could be given, but I will only refer to a recent experiment of Sir Wm. Palliser, the report of which is taken from the United Service Gazette of Dec. 26th. “Several rounds were fired from a Palliser gun which was double loaded in each case. The last round consisted of ten pounds of powder and a 66 lb. shot, then another charge of ten pounds of powder with another 66 lb. shot. Both projectiles were fitted with the service gas check, recoil tremendous, but gun remained upinjured. This gun is a 32 pdr. cast iron smooth bore converted into a 64 pdr. rifle by lining with a tube two inches thick, and weighs only three tons. The previous history of the barrel of this gun is somewhat remarkable. It formerly belonged to another 32 pdr. which it converted into a 64 pdr. rifle, and was tested by firing excessive charges ; next a series of shells, filled with powder, was purposely burst inside it; and, finally, it was deliberately
*In the case here cited with the Parrolt gun the diminished pressures were seen from the decreased expansion of the rotating band as the projectile was separated from the charge, while recent experiments with the "Thunderer's" gun No, 2, where pressure gauges were used, gave the same results.
tested to destruction by charges of increasing severity. Towards the end of the programme it fired five rounds of thirty pound charges of R. L. G. powder and 100 lb. rifled shot. At last the wrought iron barrel bulged to the extent of one quarter of an inch, and cracked the casing harmlessly through a hole that had been bored into it near the trunnions, the charge being thirty pounds of R. L. G. powder and a 150 lb. shot. The bulged barrel was then taken out of its casing, and the bulged part, two feet long, was bored out. A new lining about one half of an inch in thickness was inserted, which brought the bore back to its original size. The external bulge was next turned off in a lathe, and the barrel was then put into its present cast iron gun.
The experiments at Sandy Hook by a Board of Army officers were rather more what would be called legitimate, and had reference to ascertaining the life-time of the converted gun. I have not the latest reports on the Sandy Hook firing, but from the last report of the Chief of Ordnance, General BENET, to which I have had access, I quote the following results :
A X inch Columbiad converted into an 8 inch M. L. R. by lining with a coiled wrought iron tube made at the Elswick gun factory in Eogland was quite serviceable after eight hundred and seventy-six rounds with 35-1b. charges and 180-1b. projectiles.
A X inch Columbiad converted into a 9 inch M. L. R. was in perfect condition after five hundred and two rounds.
Another X inch Columbiad converted into an 8 inch M. L. R. with a tube made by the West Point foundry looked better after five hundred rounds than the English tube after the same number.
A X iuch Columbiad converted into an 8 inch M. L. R. by lining with a steel tube blew to pieces after four hundred and fifty six rounds. From all this it may well be claimed that the Bureau of Ordnance did not proceed to the conversion of its XI inch S. B. guns into 8 inch rifles without knowing what to expect of them, and we see the announcement of the proposed conversions in the report of the Secretary of the Navy for 1875 where he says " that the necessity of arming some of our ships with rifled cannou is so obvious and pressing that, pending the construction of new guns, the Department proposes to convert a limited number of XI inch S. B. into safe and efficient rifles, by the insertion of wrought iron tubes, the recent conversions made by the Army Ordnance having clearly determined the practicability of making them with safety and certainty.”
Let us pass now from the strength and safety of this system to the increase in power and efficiency of the rifled gun over the original smooth bore.
A comparisou of the muzzle energies of the XI inch S. B. and the 8 inch R., the former with a solid shot of 166 pounds and the latter with a battering shell of 180 pounds, shows in foot tons 2627 to 1300 in favor of the rifle, or about twice as much. In shell firing we have in the smooth bore a shell of 136 pounds, with a six pounds bursting charge, and in the rifle a shell of 180 pounds, with an eleven pounds bursting charge. The muzzle energies with service charges are still in favor of the rifle, -1798 to 1446 foot-tons. At 1000 yards, 1397 to 648. At 2000 yards, 1179 to 322. The trajectory of the rifle shell is much flatter, giving a less angle of fall, and consequently increasing the dangerous zone. At 2000 yards, for example, it is for the rifle, 5° 14', and for the smooth bore, 10° 48'.
The tubes are made at the West Point foundry, Cold Spring, N. Y., and, briefly, the process is this : bars of carefully selected and worked iron, of about thirty-six feet in length, are heated to a good red, in a long blast furnace, and then rolled up over a revolving mandrel, six and one-half inches in diameter and slightly tapering towards one end. This leaves a spiral coil, which is brought up to a welding heat in another furnace, put into a pot and "coil welded,” as it is called, under the hammer. Two of these welded coils are then welded together, and the whole becomes a "section:" two sections give the required length of tube. The lower end of the tube is turned down, and a jacket, made in the same manner as the rest of the tube, is shrunk on with moderate tension. Between the inner tube and jacket runs a spiral gas channel, which comes out at the bottom of the tube and communicates with a gas channel through the casing or gun proper. This would become a tell-tale in case of a rupture of the inner tube along the powder chamber and seat of projectile. The end of the tube is closed with a screw plug. The tube, having successfully passed a water proof, is rified and turned down to thirteen and a half inches, when it is inserted in the gun, which has been bored out to that diameter, with a clearance that must not exceed .007 of an inch at the lower end nor.015 of an inch at the muzzle. The tube is secured in the gun by a muzzle collar, and from turning, on account of rifling, by a securing pin at sixty inches from the muzzle. As lining the XI inch gun in this way throws the center of gravity forward, giving a muzzle preponderance, the truonions are turned down from a center forward of the old one, and by then putting on eccentric composition rings the center comes one and a half inches forward of the original one and gives the gun a breech preponderance of about 280 pounds. The weight of the gun will average about 17, 360 pounds. The rifling is a uniform twist of one turn in sixty calibers, fifteen lands and fifteen grooves, equal in width, and .075 of an inch depth of grooves.
In proof firing the charge of twenty pounds of hexagonal powder was hardly sufficient to set out the walls of the tube; but with the 35-1b. charges now used the tube is thoroughly set out, showing that the pressure on the cast iron casing is due to the extra fifteen pounds. After proof; it is impossible to get the tube out without boring. A 10 inch rifle blew out the forward end of the tube during proof trial, at Sandy Hook, owing to a defective weld in the tube, which was made in England. Attempts were made to pull out the breech end, and the force from six sixty-ton jacks applied, but to no purpose. It was then bored out.
As to the range of this gun, the whole question is one of opinion as to what is required in naval shell firing. Actions where this class of gun would be of any great use are not likely to be fought at over one thousand yards, and the real damage heretofore done by shell guns in Daval engagements has been within that distance. What we want, therefore, is a shell of the largest possible capacity to be accurate at that distance. We can well afford to sacrifice a few hundred yards of range in order to throw a mine of powder into an enemy's ship. The English are firing a four caliber shell for that purpose, and report the accuracy as quite satisfactory up to two thousand yards, although the flight is somewhat noisy. Our shell is but 2.8 calibers, as our pitch of rifling is somewhat slower than the English, and is also satisfactory for the same distance.
Our battering shell of 2.5 calibers with the 35 Ib. charge has an excellent flight for four thousand yards and upwards, and the new common shell lately ordered are for the consolation of those who prefer accuracy to power, and will also be of 2.5 calibers. It was supposed by many officers who used the 8 inch rifle for the first time, firing low charges with long shell, that the unsteady flight after the first five or six hundred yards was a great defect, but the shell was carrying about eleven pounds of powder as a bursting charge, and the accuracy was good, as I said before, for the ranges contemplated. The shell were reported as tumbling, but from my experience at the proving ground at Nut Island, where we fired at a distant target, the shell merely wabbles. There was apparently a center of gyration that developed itself as the velocity decreased, and gradually came farther and farther to the rear from the frout as the shell went on, increasing