Calibre

“ Rifle, s. A gun whose barrel is only constructed to shoot bullets.
I have made many experiments, and thought a good deal, by way of ascertaining the best calibre for answering the particular or general purposes to which the rifle may be applied. We all know that the resistance of the air is the chief obstacle which projected bodies have to encounter. ”

“ As an example of an identical force acting during periods of time successively equal to 1, 2, or 3, we may take three guns of the same calibre, but of lengths equal to 1, 2, and 3, and of which the charges, or rather, their propulsive forces, are identical and constant. ”

“ By putting this weight of ball into a conical form of good proportions, the calibre of the gun may be made about ninety gauge. which, for a range of four hundred yards, cannot be excelled in accuracy with that weight of gun.
But in a rifle the grooving is of the utmost importance; for velocity without accuracy is useless. ”

“ Shell-guns are always to be denominated by the diameter of the bore; shot-guns by the weight of their shot.
48. Guns of the same calibre and class, when it can be conveniently done, are to be stowed in the same tier or range, and those of each class belonging to or selected for any particular vessel kept together. Each tier or range of guns of a particular calibre or class is to be marked accordingly with paint on a sign-board, and the first gun of each class belonging to a vessel is to be marked with the name of the vessel. ”

“ In a defensive position, the guns of the largest calibre should be posted on the weakest points of the line, and on those from whence the enemy can be discovered at the greatest distance. Those heights on which the enemy in advancing may rest his flanks, and those from whence he may be fired upon obliquely, must also be occupied by the largest calibres. ”

“ Free from the defects named in the following rules for the use of the inspecting instruments:
FOR SHOT.
70. Inspecting Instruments.—One large, small, and one medium ring gauge, and one cylinder-gauge for each calibre. The cylinder-gauge shall have the same diameter as the large gauge, made of cast iron, and three calibres in length. One hammer weighing two pounds, and having a flat face and a conical point; one searcher, of steel wire, with a handle; one pair of calipers and standard scale; one cold chisel; steel punches. ”

“ Another method of measuring the quality of armour, which is largely employed upon the continent of Europe, is by the ratio, r, between the velocity requisite to perforate any given plate and that needed to pierce a plate of mild steel of the same thickness, according to the formula of Commandant Jacob de Marre, viz. v = Ae0·7·a0·75/p0·5 where e = the thickness of the plate in centimetres, a = the calibre of the projectile in centimetres, p = the weight of the projectile in kilogrammes, v = the striking velocity of the projectile in metres per second, and log A = 1·7347. ”

“ It must be remembered that a gun varies as the cube of its calibre. A 12-inch piece is not twice as powerful as a 6-inch. It is eight times as powerful. The howitzer [Pg 176] could now fire from an immense distance. ”

“ Those, therefore, the calibre of which does not exceed a pound bullet, are termed small-size Rockets; those whose calibre is from one to three pounds are of the middle size; and those whose calibres exceed the last dimensions, are termed Rockets of the [84] largest size ”

“ The size of opening which a bullet of given calibre will make through wood depends upon the distance of the weapon, the firing charge, the velocity of the bullet, the extent to which its shape has been altered by passing through the given barrier, by the heat of the explosion, by the impact of the air upon the heated and consequently softened metal, and by the density and thickness of the wood, as well as by the resistance which it may have offered mainly from its being fixed in place or movable. ”

“ Even in a dead calm no satisfactory shooting can be done beyond two hundred yards with a lighter ball than half an ounce, and any one who becomes interested in rifle-practice will soon grow impatient of being confined to short ranges and calm weather. This brings us, then, to the question of calibre, which I conceive to be the first one to be decided in selecting a gun, and the decision rests upon the uses to which the gun is to be applied. ”

“ Pondering the matter, perhaps more than it warranted, I turned to the dresser. The only detail here worth a passing notice was a small pasteboard box containing a number of .38 calibre cartridges. Originally there had been fifty in the box. I counted them. Six were missing; just the number required to charge the cylinder of most revolvers of the same calibre. ”

“ A rifle may perform first rate at short ranges, and fail entirely at long, while a rifle which will fire well at extreme ranges can never fail of good shooting at short. In fact certain calibres, &c., &c., &c., perform best at certain distances, Points in a perfect rifle.and in the combinations of a perfect rifle there are certain points to be attended to, or the weapon will be deficient and inferior. ”

“ The following table gives the increase obtained at successive stages in the development of the power of the 80-ton gun, which was first under-bored for experiment, and gradually brought to its present dimensions : Table showing Experiments with 80-ton Gun. Powder, Service P 2 (-incli cubes) . Calibre. Diam. of Chamber. Weight of Charge. Density of Charge. Weight of Projectile. Mean Pressure in Chamber. Muzzle Velocity. Muzzle Energy. Muzzle Energy per Ton of Mean Pressure. 1 enetrating Power into Armour at 1000 yds. Thickness of Armour which would be pene trated at 1000 yds. ”

“ Our gun-makers use from six to ten grooves.
To sum up our conditions,—the model rifle will conform to the following description:—Its weight will be from ten to twelve pounds; the length of barrel not less than thirty inches, [1] and of calibre from ninety to sixty gauge; six to ten freed grooves, about .005 inch deep, angular at bottom and top, with the lands of the same width as the grooves; twist increasing from six feet to three feet; barrel, of cast steel, [2] fitted to the stock with a patent breech, with back action set lock, and open or hunting and globe and peek sights. Mr. ”

“ 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. ”

“ Experience alone will enable you so to proportion your charge [260] that you shall come at the full powers of which your gun is capable. The gauge, the length, the weight—all must be taken into account, and provided for. For the ordinary run of fowling-pieces, the following is a fair proportion:—A shot-charger that holds an ounce and a half of shot may be filled to the brim with powder, which wall serve to load with, as also to prime: the same measure filled up with shot will constitute your charge of lead. ”

“ There are several ways of making a test, but I have one of my own. I am going to take a solid block of steel, of known weight—say about a hundred pounds. This I will put into a sort of square cylinder, or well, closed at the bottom somewhat like the breech of a gun. The block of steel fits so closely in the square well that no air or powder gas can pass it. ”

“ When this is clear, proceed, "Now, suppose a man is shooting at a mark about the size of a quart can. His rifle carries perfectly more than 100 yards. With such a gun is it any harder to hit the mark at 100 yards than it is at 50 yards?" ”

“ The charge, and elevation being known for any range, when the gun and parapet are on the same level, the same charge, and elevation may be used so long as the difference of level does not exceed one-twentieth of the horizontal distance between them, the elevation being given by the tangent scale, and the gun laid at the parapet, whether above or below its own level. ”

“ How do the diameter and weight of the projectile affect the range?
As the ball increases in size and density, it will overcome with more ease the resistance of the air.
11. Does the inclination of the line of sight to the horizon have much effect on the point-blank range?
Only when this inclination is very considerable. For the ordinary inclination, from 0° to 15°, above or below the horizon, the difference may be wholly neglected.
12. What is the effect on the point-blank range of firing upwards under a large angle? ”

“ That the charge being the same, very little is gained in the range of a gun, by a great increase of its length; since the range or amplitude is nearly as the fifth root of the length of the bore, and gives only about a seventh part more range with a gun of double length. ”

“ In scribing a circle with a pair of dividers mark the center with your center punch first as this will prevent your dividers from slipping.
(10) Inside calipers are used for measuring the inside diameters of cylinders and the like, and, conversely (11) , outside calipers are used for measuring the outside of anything that is round. In either case you measure the distance between the points of your caliper with your rule to find the diameter of the thing. (12) A center punch is always useful to make [62] a starting point in metal with, for it can’t be rubbed off or lost sight of. ”

“ If there were less than six men within six inches of a gun, then we tried letting it fire as many shots as there were men, and we permitted a single man to move a gun, and move with it as far as he could go by the rules--a foot, that is, if he was an infantry-man, and two feet if he was a cavalry-man. ”

“ Tangent practice with 8-inch Guns, weighing 65, and 60 cwt., carrying a single shot weighing 56 lb., or a shell weighing 56 lb., and charged with 10 lb. of powder. The line of sight is parallel to the axis of the bore, and the gun is 5 feet 4 inches above the level of the water. ”

“ As I understand it, you are proposing a set of equations which will show the range of any weapon by computing the weight of the ball against the weight of the powder. (Perhaps I err here, but that is my understanding.) It seems to me that you are building a castle-in-Spain on rather insubstantial ground. Where is your data? What research have you done on cannon-fire? Without a considerable body of facts to work with, such broad generalisations as you propose are quite out of order. ”

“ Scale-armor. Consisted of small plates of steel riveted together in a manner resembling the scales of a fish. From the small size of the plates, it possessed considerable pliability, and was therefore a favorite protection for the neck, in the form of a curtain hanging from the helmet. Scale-armor is now obsolete, except, perhaps, among some Eastern potentates.
Scaling. Scaling a piece of artillery, is the flashing off of a small quantity of powder to clean out the bore; about one-twelfth of the shot’s weight. ”

“ What are the dimensions required for an earthen parapet to resist the fire of field or siege guns?
6 feet for 6-pdrs.; 14 feet for 12-pdrs.; 18 feet for 24 or 18-pdrs.; four feet of oak or brick will resist cannon shot.
33. What thickness of ice will admit the passage of infantry, cavalry, and artillery?
Ice 3 inches thick, will bear infantry marching in file; from 41⁄2 to 61⁄2 inches, cavalry and light artillery; and beyond that the heaviest gun carriages may pass in safety. Ice 8 inches thick will bear nearly 10 cwt. upon a square foot without danger. ”

“ It follows from the foregoing that the length of bore which corresponds to a maximum velocity depends upon the projectile, charge of powder, and material of which the piece is made, and taking the caliber as a unit of measure, it is found that this length is greater for small-arms which fire leaden projectiles than for guns which fire solid iron shot, and greater for guns than for howitzers and mortars, which fire hollow projectiles. ”

“ The Measure is taken from you to the Enemy, and from the Enemy to you: The first is easier known, as well because it is naturally so, as by the Custom of your Lunge, which being, in regard of yourself, always the same, makes it easier by Practice: The Measure from the Enemy to you is difficult, from the Difference in Persons whose Stature, Activity, or Swords, are not always alike; and tho' the Height shou'd be the same, the Arms, Thighs and Legs are not proportionable; besides there are big Men that have short Arms, and little Men that have long Arms. ”

“ Now, take a rifle with a very curved trajectory, say one whose bullet, at the highest point of the trajectory corresponding to a range of 500 yards, is 10 feet above the line of sight. There will be a large extent of ground between the target and the rifle that is not danger space for a target 2 feet above the line of sight. ”

“ Proving the Size during Boring.—A method of proving the size of the interior of the barrel and at the same time test its being perfectly of the same size throughout, is to cast an ingot of lead about an inch long in the muzzle, and with a rod forcing it through. ”

“ Run the finger to the given range on the range-arm.
Third: The azimuth difference is read on the nearest circle that cuts the point where the finger last rests, and the range difference is read on the scale in red ink along the azimuth circle of the board. (See Fig. 77.)
Q. What is meant by muzzle velocity?
A. The number of feet per second a projectile is moving at the time it leaves the muzzle of the gun. It is also called Initial Velocity.
Q. From the following gun commanders' range-scale find the time of flight, sight elevation, and quadrant elevation for 4120 yards range. ”