[Ill.u.s.tration: RAPID-FIRE GUN

Six-inch rapid-fire gun equipped with patented two-handed elevating gear, consisting of two hand wheels on opposite ends of the same shaft, the handles being 180 degrees apart. The pointer uses both hands in elevating and depressing the gun. The electric firing trigger _A_ is worked by the index finger of the right hand without releasing the handle. There is a second firing handle _B_ attached to the slide, for firing either electrically or percussively.

_Courtesy of the Bethlehem Steel Co._]

Built-Up and Wire-Wound Guns.

A built-up gun is made of several layers of forged steel. The parts of such a gun are known as the liner, the tube, the jacket and the hoops.

The liner is a single piece which extends the length of the bore and is intended to contain the rifling and the powder chamber. This is inclosed by the tube, which is also in one piece, surrounding the liner throughout its length. Outside this is the jacket, made in two pieces and shrunk on the tube. Over the jacket lie the hoops, six or seven of these being used in a big gun. Like the jacket, these also are shrunk on. All these parts are made of the finest quality of open-hearth steel.

[Ill.u.s.tration: FIVE-INCH NAVAL GUN AND MOUNT

The latest type of gun used in the U. S. Naval Service in the secondary batteries on a battleship.]

[Ill.u.s.tration: COAST DEFENSE GUN

A modern 14-inch coast defense gun at Sandy Hook. The gun is mounted on a disappearing carriage, which lowers it out of sight behind the breastworks after firing. This is one of the most powerful guns in the world, firing a projectile which would pierce the armor of a battleship more than five miles away.]

[Ill.u.s.tration: _Copyright by Underwood & Underwood, N. Y._

A BATTERY OF 12-INCH COAST DEFENSE MORTARS

These powerful weapons fire a projectile which weighs from 700 to 1,046 pounds, depending on the range desired, and which is capable of piercing the deck armor of any battleship. They have a range of 20,000 yards with the 700-pound projectile. The gun is 16-2/3 feet long and is fired only at elevations between 45 and 65.]

[Ill.u.s.tration: GIANT GUNS--THEIR MUZZLE-ENERGY, PROJECTILES, AND PENETRATING POWERS

The British 13.5, which was known as the 12-inch-A until the "Lion" was launched, has a length of 45 calibers, and a muzzle-energy ten per cent greater than that of the 50-caliber 12-inch of 1909 and 1910. It may be noted that the caliber is the diameter of the bore of a gun. The statement that a gun has a length of 45 calibers, for example, implies that the gun is forty-five times the bore's diameter. Thus a 12-inch gun of 45 calibers is 45 feet long.]

These pieces are prepared with the utmost care to prevent any defective material entering into the make-up of the gun. After the parts are put together a thorough forging follows, either by use of hammer or press, the latter being now used in preference. The usual practice in forging is to continue it until the ingot is decreased to one-half its original thickness and is within two inches of the desired diameter of the finished work. It is then annealed with great care to relieve the strains set up in the metal by the forging and next goes to the machine shop to be rough bored and turned. The final boring takes place after a second annealing. The above is only a rapid sketch of the total process, in which elaborate care is taken to prevent imperfection of any kind.

[Ill.u.s.tration: ORDNANCE PROVING GROUND

View showing smoke cone occurring during the proof firing of a twelve-inch gun with brown powder.

_Courtesy of the Bethlehem Steel Co._]

In a wire-wound gun an inner tube of steel is thoroughly wrapped by successive layers of ribbon wire, each layer being wound with wire at a different tension. This type of gun is preferred by foreign manufacturers, but within the United States the built-up system is in higher favor and is almost exclusively employed. The makers of the wire-wound cannon claim for it a positive soundness of material impossible to secure in a built-up gun, and that it has greater firmness of material and superior tangential strength. But with this come certain disadvantages, a notable one being a lack of rigidity in the longitudinal direction, this tending to increase the "droop" of the muzzle and give a certain "whip" to the piece when fired that reduces accuracy. This and other disadvantages have given the built-up guns general preference in this country, they being found strong enough to bear any pressure desirable in service. In addition they are much cheaper to build than the wire-wound guns.

Modern heavy guns are made of medium open-hearth carbon steel, forged as stated. The liner and tube are then placed upright in an a.s.sembling pit, the jacket and hoops shrunk on, and the finishing work done, as above said, the breech mechanism being finally fitted. Within recent years there has been a steady increase in the size and range of cannon, until an immense size and weight have been attained. For naval purposes the 14-inch gun is the largest now used in American battleships, but in the United States coast defense forts, 16-inch guns are installed. England has equipped several of her latest battleships with 15-inch guns and other nations are following in the same direction. In recent great battleships four turrets are used, each carrying three of these great guns, giving a broadside of twelve of these monster weapons of war. Of the three guns, the middle one is raised above the line of the others. A battleship thus armed is able to fire six guns ahead and six astern by raising the second and third turrets so as to fire over the others.

[Ill.u.s.tration: FOUR-INCH FIFTY CALIBER RAPID-FIRE GUN ON PEDESTAL MOUNT

Extraction of cartridge case by opening of breech mechanism. Weight of gun, 6,170 pounds. Length of gun, 205 inches (51.2 calibers). Weight of projectile, 33 pounds. Travel of projectile in bore, 165.6 inches (41.4 calibers). Weight of charge, 15 pounds of smokeless powder. Muzzle velocity, 2,900-foot seconds. Muzzle energy, 1,928-foot tons. Weight of mount with shield, 9,470 pounds. Thickness of shield, 2 inches of nickel steel. Gun equipped with telescopic and night sights and with electric and percussion pull-off firing gear.

_Courtesy of the Bethlehem Steel Co._]

Military cannon are divided into three cla.s.ses, based upon the length of caliber, and technically known as guns, mortars and howitzers. In guns the length is relatively great, in mortars relatively small, compared to their calibers. Howitzers form a cla.s.s between guns and mortars in length. The field guns of the American army are the 3.6-inch breech-loading mortars, and the 3.6-inch heavy and 3.2-inch light guns.

The siege guns in the service are the 5-inch siege guns, the 7-inch howitzer, and the 7-inch mortar. The coast defense artillery consists of the 8-, 10-, 12- and 16-inch guns and the 12-inch mortars. In the recent European war very heavy cannon were used for field service, pieces of the size usually placed in forts being drawn to the field by powerful tractors, set on concrete platforms and used in attacks on fortified cities. It was through the use of such ordnance that the German army so easily reduced the strongly fortified Belgian cities.

[Ill.u.s.tration: FLUID COMPRESSION PLANT

While still in a molten condition in the mold, the steel used in manufacturing guns and shafting is subjected to hydraulic pressure until the ingot has cooled, thus insuring the solidity of the metal. The upper head of the compressor weighs 125 tons, and the lower one, including the cylinder through which the hydraulic pressure is applied, 135 tons.

_Courtesy of the Bethlehem Steel Co._]

[Ill.u.s.tration: AMMUNITION.[32] (See page 410.)]

[Ill.u.s.tration: TWO-HANDED ELEVATING GEAR.[32] (See page 410.)]

[Ill.u.s.tration: RANGE FINDER AND PREDICTOR; HOME AND DISTANT STATION INSTRUMENTS.[33]

(See page 410.)]

[Ill.u.s.tration: ARMOR PIERCING PROJECTILES, CAPPED AND UNCAPPED.[33] (See page 410.)]

[Ill.u.s.tration: RANGE FINDER AND CHART ATTACHMENT[34]. (See page 410.)]

[Ill.u.s.tration: EIGHTEEN-INCH, THIRTY-CALIBER TORPEDO GUN.[34] (See page 410.)]

[Ill.u.s.tration: FIRING GEAR FOR GUNS.[35] (See page 410.)]

[Ill.u.s.tration: FUSES.[35] (See page 410.)]

The range of these giant cannon is enormous and their destructive power great, this being added to by the fact that the explosive sh.e.l.l has replaced the solid round shot of old-time gunnery. A 14-inch gun of 45 caliber can discharge a 1,400-pound projectile at a muzzle velocity of 2,600 feet per second. If we compare this with a locomotive going at the speed of sixty miles an hour, we have in the latter a speed of eighty-eight feet per second to compare with the 2,600 feet per second of the cannon ball. From this we can well conjecture the vast speed with which the latter moves, its enormous range and vast powers of destruction.

[Ill.u.s.tration: THREE-INCH HORSE ARTILLERY GUN, LONG RECOIL CARRIAGE AND LIMBER

Length of gun, 85 inches (28 calibers). Weight of projectile, 12 pounds.

Travel of projectile in bore, 74.65 inches (24.88 calibers). Weight of charge, 17.1 ounces of smokeless powder. Muzzle velocity, 1,750-foot seconds. Muzzle energy, 255-foot tons. Weight of gun, carriage and limber, containing 36 rounds of ammunition, 3,355 pounds. Ground clearance, 18 inches.

_Courtesy of the Bethlehem Steel Co._]

As facts are better than theories, it will be of interest to adduce a recent example of gunnery of a most illuminating type, but as regards distance and remarkable accuracy of aim. In September, 1916, the American battleship "Pennsylvania," armed with a main battery of twelve 14-inch guns, fired these simultaneously at a target in the Chesapeake 22,000 yards, or more than twelve miles, away. The target was the sunken hulk of the "San Marcos," formerly the battleship "Texas," which for several years had been used for similar purposes. As the target was invisible to the gunners it was hardly to be expected that any of the shots should fall near the target. But the extraordinary result appeared that five of these twelve shots struck the hulk. As each of these projectiles weighed 1,400 pounds any battleship receiving such a broadside would probably have gone promptly to the bottom. The result, which has never before been equaled in accuracy, sufficiently attests the remarkable proficiency in range-finding that modern engineers have developed.

As for the penetrating powers of such huge shot we may take the 15-inch gun, the type of the largest guns in our fortifications and which is claimed to be able to pierce sixteen inches of armor at a range of 18,000 yards and ten inches at a range of 20,000 yards. A notable example of this took place on September 15, 1916, at the proving grounds at Indian Head, on the Potomac River, when a 16-inch, 2,100-pound, solid steel sh.e.l.l, said to be the first ever fired from a naval gun of that caliber, with a small charge of explosive, went through a plate of armor, penetrated a thick sand backing, and continued its course, striking the house of an employee of the proving grounds and plunging through the kitchen rending all before it. This was a naval gun, the largest yet made for naval purposes.

[Ill.u.s.tration: PATENTED CHAIN RAMMER

As applied to loading twelve-inch turret guns. The s.p.a.ce occupied by this rammer in the rear of the gun is less than one foot, with a possible ramming stroke of fifteen feet. The rammer being attached to the gun's cradle or slide, moves with the gun in elevation and depression. The ammunition car also moves with the gun. Loading can be performed while the gun is kept in motion following a moving target.

This rammer is stiff in all directions when extended.

_Courtesy of the Bethlehem Steel Co._]

In the make-up of modern guns the breech-loading mechanism is of essential importance, it being necessary that the breech should be capable of rapid opening for the insertion of the charge into the loading chamber, as rapidly closed and firmly secured to prevent it being forced open by the reaction of the discharge. It also must fit with such tightness as to prevent any escape of the gas in that direction, and force it to exert all its impelling power upon the ball.

Various methods are used for this purpose, with the result that loading and firing can be very quickly and effectively performed. In the case of guns in fortifications, the disappearing carriage is a highly important invention of recent date. By its aid the gun is quickly lifted to fire over the walls of the fort and is driven backward by the force of its discharge, sinking to a place of safety behind the walls. This saves the gun and its crew from injury by return fire.

We may say in conclusion that the great European war was notable for the use of artillery to an extent far surpa.s.sing its employment in any previous war. This great conflict, indeed, was very largely a contest of gun fire, in which the opposing fields of the battling armies were so swept with sh.e.l.ls and other explosives as to render life impossible on the open land, trench digging being one of the main employments of the embattled hosts. Never before had the supreme value of gunnery in warfare been so fully demonstrated.