ohland
06-26-2015, 09:10 AM
This is a period article, clumsily transcribed and provided for your edification.
NOTE: I had to delete all the tables (Velocity, Striking Power, and"C" table) because it would not fit. (23K characters vs 20K character limit). As things progress, I want to start a Kephart collection on my experiences page so you all can SEE the data. v/r, Lūb Monkey
Outing, vol 75, no. 2, Nov 1919. Pages 81-83
https://books.google.com/books?id=BRALAAAAIAAJ&pg=RA1-PA67&dq=outing+vol+75+%22the+best+form+of+bullet%22&hl=en&sa=X&ei=MD-NVfSXFcSkNsj6gpgM&ved=0CB0Q6AEwAA#v=onepage&q=outing%20vol%2075%20%22the%20best%20form%20of%20 bullet%22&f=false
By Horace Kephart
Objections to the Square Base and Arguments in Favor of the Boat-Tailed Variety
ABOUT thirty years ago I got the idea into my head that we were shooting our bullets wrong end foremost. And I still think so. A bullet with flat base and tapered point is butt-heavy. According to the laws of nature the center of gravity of a projectile should be forward of the center of form.
If we should shoot a flat based bullet point foremost from a smoothbore gun, gravity would draw the heavy butt down and tilt the point up, but the force of propulsion would tend to throw the butt forward and the point to the rear. These two forces, plus air resistance, would make the bullet tumble and fly wild.
The only way to defeat these natural tendencies, and make the bullet fly point-on, is to give it a rapid spin on its longer axis, like a top. Even a round ball requires some spinning motion, because it cannot be made perfectly smooth and symmetrical, nor of exactly uniform density throughout. But it need not be spun nearly so fast as a bullet with flat base and tapered point. The twist of rifling for a .30 caliber round ball may be no quicker than one turn in five feet, whereas for a .30 Springfield bullet it must be one turn in ten inches. This is partly due to the length of the modern bullet, but also in part to its ill balance, with center of gravity away to the rear.
If a long bullet were so shaped that its center of gravity was forward, as in an arrow or a cross-bow bolt, a slower twist of rifling could be employed. There would be less torsion and friction of bullet and barrel. The projectile would "steer" better, and it would "buck the wind" better.
This is assuming that the point-heavy bullet had proper stream lines, and that it had true delivery from the gun's muzzle.
In the days of my rifle apprenticeship I knew nothing about the science of ballistics. Neither did I know anything about the history of firearms. I had never heard of Benjamin Robins, the father of modern gunnery, who, away back in 1742, recommended an egg-shaped projectile, to be shot heavy end foremost from a rifle barrel, for ranges beyond what the round ball could attain. He demonstrated its superior ballistics mathematically. But nobody would listen to him, and his idea was entombed amid the musty archives of the Royal Society. Perhaps some Chinaman perpetrated the same heresy in the days B. C, and was bastinadoed or beheaded for it.
Having no mathematics to back my own theory, I took some 500-grain Springfield bullets of .45 caliber and had their bases turned hemispherical on a lathe, leaving only two cannelures besides the shoulder bearing. These I shot butt end foremost, with full charges of black powder. There was no noticeable tipping, and no sign of abnormal pressure. I used no sabot or other wad.
Then I tried to get somebody to make me a mould to cast "double pointed" bullets of my own design; but no one would fool with such a thing. I was laughed at, or argued out of countenance, by men who were considered experts.
Many years later I saw an excerpt from an ordnance report on tests of torpedo-shaped projectiles. They were condemned as impracticable; but I believed that their inaccuracy was due to faulty design which failed to insure true delivery from the muzzle. I thought this mechanical defect might be remedied. The tests proved at least that such bullets did maintain their speed and energy much better than flat based ones, with consequent lowering of trajectory.
Then I wrote an article defending the principle of streamline design for projectiles. It was published in Arms and the Man, August 1, 1907, under title of "The Bullet of the Future." The only comment that I ever heard on it was that the idea was fanciful, impracticable, unscientific. "There is no vacuum following a flying bullet." "What can a vacuum do, anyway: it's simply a hole, a nothing and can exert no drag nor any other force." "Air is not inelastic, like water, and your comparison of bullet to boat is no analogy at all." "The air thrown aside by a bullet's point cannot bound back again quick enough to exert any forward push on a tapered tail." These were some of the replies.
My article was based only on crude experiments, observation of the conduct of air under tornado pressures, and pure reason. Let me repeat a few of the paragraphs, as they were written for common riflemen like myself, and I cannot improve their clarity in common terms:—
“I have long been of the opinion that a bullet of radically different form from any hitherto used would outclass any and all flat-based bullets, if we found proper means of delivering it from a gun suitably rifled... My belief is based upon study of the behavior of air under high pressure, comparing it with water, and considering the lines of a bullet as we consider the lines of a ship...
Ordinarily we are accustomed to think of the atmosphere as merely a tenuous gas, or combination of gases, easily displaced by any body in motion. But when a storm comes up we think of it as something different. We all know what a wind of 100 miles an hour can do to trees and houses. Now the pressure against those trees and houses would be the same if they were moving at the rate of 100 miles an hour through still air. Here we are considering a speed of only 147 feet a second.
When the wind rises to a higher velocity than this, it begins to do things that we would hardly believe until we saw them. I have been through hurricanes on sea and land, but I never fully realized what high air pressure meant until I picked myself up out of the debris of the St. Louis tornado of May, 1894. If you have ever stood in the wake of a tornado, looking at pine scantling driven through steel girders, straws and chicken feathers stuck into fence boards, locomotives tossed into ditches, steel rails torn up from the ties and twisted like molasses candy, you have a vivid idea of what the wind can do when it gets real mad.
Very well, the bullet of our new Springfield rifle starts from the muzzle at a speed fifteen times greater than that of a hurricane. Think, then, of the atmospheric resistance that it must encounter.
When we see a blast of air do the work of a water blast, we may say that air under such pressure is in a state more like water than like the thin air that we breathe.
Let us turn now from bullets to boats, by way of illustration. Everybody knows that the ease or difficulty with which a boat can be propelled through the water depends very much upon the shape of the under-water part of the hull. Nobody would think of building a boat like a box, with square ends and no rise. A log, with ends sawed off square, will push or tow more easily than a squared timber of equal displacement. If we sharpen the front end of the log, like a modern bullet, it will go easier; but we will still have an absurd design for speed. The maker of a dugout tapers both ends of his craft. Why?
You begin to glimpse the idea. It is not necessary to go farther with this boat illustration, save to mark one other fact, which is of vital consequence in our discussion. The difference in lines, of various types of boats, becomes of more and more consequence as the speed increases. No power that could be put aboard could ever make a scow or a canal boat shoot through the water like a torpedo boat of like displacement. The higher the speed intended, the nicer study must be given to the vessel's proportions. The same rule holds good in the case of projectiles designed to be shot through the air..
.
Is only the point of the projectile to be considered? How about its sides and rear?
A ship intended for high speed would not be built with square stern below the waterline— that would be an absurdity. Now a bullet is entirely immersed in the medium through which it travels, like a submarine boat or an airship. Would any one dream of designing either a submarine or an airship on lines like those of a Krag or Springfield bullet? Manifestly not. The flat base of such a body would offer a heavy drag, even at low speed, and the form would be so ill-balanced as to be unmanageable.
I think that even a novice can now see that the ideal form for a bullet would be something like a spheroid or a circular spindle (something like a motor torpedo), but slightly thicker at the forward end, so as to throw the center of gravity forward. A bullet of such form would "slip through the air" more readily than a spitzer bullet, it would maintain speed much better, it would drift less, would be less influenced by contrary winds, and, having no tendency to tumble butt-foremost, it would require a slower twist, and would need no mantel, thus saving wear, and making the gun easier to clean.”
I presented with this article a sketch of a suggested bullet, rounded at both ends and sloping thence very gradually to the shoulder or bearing surface, the forward part being of enough greater diameter than the rear to afford a square shoulder as positive gas check, the bearing here being slightly above true caliber of barrel to bottom of grooves. A sabot, or cup-wad was shown therewith, but I said that whether it would be useful or not would have to be determined by experiment. I doubted it.
This was the first time, to my knowledge, that such an argument was advanced in a sportsman's journal. It passed with little comment at the time; but much has been published on the subject of "boat-tailed" bullets within the past four or five years, especially since it was learned that Switzerland, then France, and afterward other nations, had quietly adopted such projectiles.
On June 8, 1918, Mr. E. Newitt published in Arms and the Man a description of the French balle D '05, with illustration drawn to scale, and ballistic data. He had tested it three and a half years earlier, in Remington rifles made to shoot the French cartridge.
"I was astonished," he said, "by its accuracy and indifference to the strong winds which prevailed during the shooting, and still more by the remarkable flight qualities indicated by the low angle of elevation required. At 1,000 yards the wind allowance was barely half that required by the Springfield, while the hitting of the 36-inch bull's eye seemed to be absurdly easy. A rifle bullet that can give the 1906 Springfield 360 foot-seconds start, overtake it at 500 yards, and beat it in every quality that constitutes excellence in a small-arm projectile, is certainly deserving of more notice than it has received in this country."
The rifle bore for this French cartridge is of .315 caliber. The bullet is 1.55 inch long. Its point is square for a diameter of .05 inch, thence tapers by a very slow curve backward to the shoulder (nearly an inch back from the point) to its maximum diameter of .3287 inch. The shoulder is square but very shallow. From here to the rear the bullet tapers backward to a diameter of .272 inch, with flat base.
The balle D '05 is made in one piece "of an exceedingly hard, tough composition of copper and zinc, much harder and stronger than the lead and cupro-nickel combination [of our bullets]; hence it is less liable to distortion in the barrel or upon impact, and its penetration and destructive capabilities are correspondingly greater." The bullet weighs 198 grains, which is 48 grains heavier than the Springfield, though the entire cartridge weighs only 23 grains more.
Ballistic data, as compared with the Springfield, are given by Mr. Newitt as follows:—
The balle D '05 has a ballistic coefficient, according to Mr. Newitt's computation, of .57. That of the Springfield is .389. This factor, commonly called C, measures the ability of the projectile to overcome the resistance of the air. The higher value of C in the French bullet is due chiefly to the tapered rear and the better distribution of mass (throwing more of the weight forward).
In the latter days of the war we learned that the fighting nations were using projectiles for artillery and small arms that had tapered bases. Although in most instances the tapered part was short, and the flat end of butt was large, yet a decided increase in range was attained, as compared with old-fashioned projectiles of similar initial velocity. The balle D '05 has a longer rear taper than most of them, but still it is far from having a true streamline shape. It is only an approximation toward the ideal form of projectile.
In November and December, 1918, when the censorship had been relaxed, Dr. J. R. Bevis, joint-author of Bevis and Donovan's book "The Modern Rifle," published in Arms and the Man a series of three articles entitled "The Tale of the Tail of a Bullet." Here, for the first time, was demonstrated mathematically the superiority of projectiles tapered at both ends, and a formula was worked out for computing their ballistic coefficients.
Doctor Bevis had already proved that the best form of head for a bullet was not conical, ogival, nor even paraboloidal, but one which is not a continuous curve in outline, and which he calls the para-ogival, head, which, in a bullet of same length as the Springfield's increases the value of C from .389 to .429, and reduces the height of the 1,000yard trajectory approximately two feet, with same muzzle velocity.
I do not know what progress has been made in actual tests of this bullet. Perhaps some difficulty may be experienced from tipping or gas leakage with early patterns, but I can see no reason why this should not be obviated. If the forward part of the bearing is made of bore diameter, so as to ride on top of the lands and insure its axis being in line with the axis of the bore before firing, and back of this the shoulder is of full groove diameter, or a bit more, to form a positive gas-check, as in the Pope target bullets, the edge of the shoulder being square with the longitudinal axis, the bullet should start true and emerge true to the line of fire. Probably no sabot will be needed.
Having reached the limit of efficiency in design of head, he now turned his attention to the tail of the projectile. By mathematical calculation he found that if the Springfield bullet were made with a pointed tail, which would eliminate the vacuum in a flat-based bullet's wake, its 1,000-yard trajectory would be reduced from 14.5 feet to 6.97 feet.
He showed, further, that the bullet's tail should taper not in a curve but in a straight line; and that the cylindrical or bearing part of the bullet should end abruptly with a square shoulder, as true as it is possible to make it, so that as the bullet leaves the muzzle the bearing against the walls of the bore shall cease at the same instant on all sides. The shoulder would also form a gas check. Its depth should not vary greatly from the depth of the rifling groove. He showed that the tail should be as short as would serve the purpose, with maximum angle of taper, and pointed, or as nearly so as practicable.
In the Doctor's own words: "The value of C for any bullet having any shaped head may be increased one hundred per cent by means of its tail. The .30-220 [Krag bullet] with its round nose may be made to have better ballistic properties than the .30-150 Springfield, if the tail is made the proper shape.
"Of two bullets having the same shaped head, and driven by equal charges of the same powder, that bullet having the tail has many advantages over the other. First, on account of its greater value of C, and its having a greater muzzle velocity due to less friction with the walls of the bore, and the greater density of loading, it has considerably greater range for the same elevation of sights, and a flatter trajectory over all ranges.
"Second, for the same causes, the boat-tailed bullet has greater striking energy and greater striking velocity. Its center of gravity is nearer the head, by virtue of which there is every evidence of its superiority in accuracy." He also demonstrated that the boat-tailed bullet drifts less in its flight than one with a flat base.
In a later article, Dr. Bevis showed that it was far better worth while to improve what I have called the "lines" of a bullet than to push its muzzle velocity much farther than our present military cartridges give. "Better ballistics—so much better that a comparison of the two is almost unbelievable—may be more easily attained by increasing C than by increasing the velocity. A bullet of proper construction may have considerably better ballistics at a less muzzle velocity, at a saving of the powder charge, with the same or less pressure, and less friction and consequent less wear upon the wall of the bore of the rifle."
When Dr. Bevis was in the Ordnance Department, during the war, he designed a boat-tail bullet, concerning which I quote the following data, compared with the Springfield.
If the center of gravity is forward of the center of form, it will steady the bullet in flight at all ranges.
Conservative folk may shake their heads in disbelief that this newfangled thing will work as well as it promises. But conservatism often is only a polite name for mental inertia, lack of vision, and plain oldfogy ism. The merits of a torpedo shaped projectile are incontestible, once it has been started straight on its mission, and somebody is bound to devise means of insuring its accurate delivery from the gun.
If we are to have any great increase in ballistic efficiency, with finer accuracy, lower trajectory, longer danger zone, superior energy and shock delivery at point of impact, it must come mainly from better bullets, instead of from speeding up the present type of bullets. With velocities of 2,700 to 3,100 feet a second we already have too much trouble from erosion, metal fouling, melted bullet cores, split jackets, swelled cartridge cases, and other nuisances. A bullet with flat base wastes too much of its energy in fighting the air and keeping from tumbling end over end.
If it pays to follow the streamline form of birds and fishes in designing the bodies of airplanes and racing cars, which meet nothing like the air resistance of a projectile from a gun, and if a dart or an arrow must be heavier at point than at butt of shaft, why should we go on stupidly forcing our bullets to fly wrong end foremost?
All that gun and powder can do is to start the bullet straight, with a certain spin, and at a certain speed. Then and thereafter its accuracy, its maintenance of speed and energy i its penetration and shock delivery, its ability to "jam the wind," depend upon the shape, balance, density, and other qualities of the projectile itself.
If we design a gun and then a cartridge that it is capable of handling, we are going tail-first. The prime problem is the cartridge, and a gun to use it is secondary, to be built according to the requirements of that cartridge. And in getting up a cartridge, the first thing to perfect is the bullet. The missile that is to do the work is the prime consideration.
NOTE: I had to delete all the tables (Velocity, Striking Power, and"C" table) because it would not fit. (23K characters vs 20K character limit). As things progress, I want to start a Kephart collection on my experiences page so you all can SEE the data. v/r, Lūb Monkey
Outing, vol 75, no. 2, Nov 1919. Pages 81-83
https://books.google.com/books?id=BRALAAAAIAAJ&pg=RA1-PA67&dq=outing+vol+75+%22the+best+form+of+bullet%22&hl=en&sa=X&ei=MD-NVfSXFcSkNsj6gpgM&ved=0CB0Q6AEwAA#v=onepage&q=outing%20vol%2075%20%22the%20best%20form%20of%20 bullet%22&f=false
By Horace Kephart
Objections to the Square Base and Arguments in Favor of the Boat-Tailed Variety
ABOUT thirty years ago I got the idea into my head that we were shooting our bullets wrong end foremost. And I still think so. A bullet with flat base and tapered point is butt-heavy. According to the laws of nature the center of gravity of a projectile should be forward of the center of form.
If we should shoot a flat based bullet point foremost from a smoothbore gun, gravity would draw the heavy butt down and tilt the point up, but the force of propulsion would tend to throw the butt forward and the point to the rear. These two forces, plus air resistance, would make the bullet tumble and fly wild.
The only way to defeat these natural tendencies, and make the bullet fly point-on, is to give it a rapid spin on its longer axis, like a top. Even a round ball requires some spinning motion, because it cannot be made perfectly smooth and symmetrical, nor of exactly uniform density throughout. But it need not be spun nearly so fast as a bullet with flat base and tapered point. The twist of rifling for a .30 caliber round ball may be no quicker than one turn in five feet, whereas for a .30 Springfield bullet it must be one turn in ten inches. This is partly due to the length of the modern bullet, but also in part to its ill balance, with center of gravity away to the rear.
If a long bullet were so shaped that its center of gravity was forward, as in an arrow or a cross-bow bolt, a slower twist of rifling could be employed. There would be less torsion and friction of bullet and barrel. The projectile would "steer" better, and it would "buck the wind" better.
This is assuming that the point-heavy bullet had proper stream lines, and that it had true delivery from the gun's muzzle.
In the days of my rifle apprenticeship I knew nothing about the science of ballistics. Neither did I know anything about the history of firearms. I had never heard of Benjamin Robins, the father of modern gunnery, who, away back in 1742, recommended an egg-shaped projectile, to be shot heavy end foremost from a rifle barrel, for ranges beyond what the round ball could attain. He demonstrated its superior ballistics mathematically. But nobody would listen to him, and his idea was entombed amid the musty archives of the Royal Society. Perhaps some Chinaman perpetrated the same heresy in the days B. C, and was bastinadoed or beheaded for it.
Having no mathematics to back my own theory, I took some 500-grain Springfield bullets of .45 caliber and had their bases turned hemispherical on a lathe, leaving only two cannelures besides the shoulder bearing. These I shot butt end foremost, with full charges of black powder. There was no noticeable tipping, and no sign of abnormal pressure. I used no sabot or other wad.
Then I tried to get somebody to make me a mould to cast "double pointed" bullets of my own design; but no one would fool with such a thing. I was laughed at, or argued out of countenance, by men who were considered experts.
Many years later I saw an excerpt from an ordnance report on tests of torpedo-shaped projectiles. They were condemned as impracticable; but I believed that their inaccuracy was due to faulty design which failed to insure true delivery from the muzzle. I thought this mechanical defect might be remedied. The tests proved at least that such bullets did maintain their speed and energy much better than flat based ones, with consequent lowering of trajectory.
Then I wrote an article defending the principle of streamline design for projectiles. It was published in Arms and the Man, August 1, 1907, under title of "The Bullet of the Future." The only comment that I ever heard on it was that the idea was fanciful, impracticable, unscientific. "There is no vacuum following a flying bullet." "What can a vacuum do, anyway: it's simply a hole, a nothing and can exert no drag nor any other force." "Air is not inelastic, like water, and your comparison of bullet to boat is no analogy at all." "The air thrown aside by a bullet's point cannot bound back again quick enough to exert any forward push on a tapered tail." These were some of the replies.
My article was based only on crude experiments, observation of the conduct of air under tornado pressures, and pure reason. Let me repeat a few of the paragraphs, as they were written for common riflemen like myself, and I cannot improve their clarity in common terms:—
“I have long been of the opinion that a bullet of radically different form from any hitherto used would outclass any and all flat-based bullets, if we found proper means of delivering it from a gun suitably rifled... My belief is based upon study of the behavior of air under high pressure, comparing it with water, and considering the lines of a bullet as we consider the lines of a ship...
Ordinarily we are accustomed to think of the atmosphere as merely a tenuous gas, or combination of gases, easily displaced by any body in motion. But when a storm comes up we think of it as something different. We all know what a wind of 100 miles an hour can do to trees and houses. Now the pressure against those trees and houses would be the same if they were moving at the rate of 100 miles an hour through still air. Here we are considering a speed of only 147 feet a second.
When the wind rises to a higher velocity than this, it begins to do things that we would hardly believe until we saw them. I have been through hurricanes on sea and land, but I never fully realized what high air pressure meant until I picked myself up out of the debris of the St. Louis tornado of May, 1894. If you have ever stood in the wake of a tornado, looking at pine scantling driven through steel girders, straws and chicken feathers stuck into fence boards, locomotives tossed into ditches, steel rails torn up from the ties and twisted like molasses candy, you have a vivid idea of what the wind can do when it gets real mad.
Very well, the bullet of our new Springfield rifle starts from the muzzle at a speed fifteen times greater than that of a hurricane. Think, then, of the atmospheric resistance that it must encounter.
When we see a blast of air do the work of a water blast, we may say that air under such pressure is in a state more like water than like the thin air that we breathe.
Let us turn now from bullets to boats, by way of illustration. Everybody knows that the ease or difficulty with which a boat can be propelled through the water depends very much upon the shape of the under-water part of the hull. Nobody would think of building a boat like a box, with square ends and no rise. A log, with ends sawed off square, will push or tow more easily than a squared timber of equal displacement. If we sharpen the front end of the log, like a modern bullet, it will go easier; but we will still have an absurd design for speed. The maker of a dugout tapers both ends of his craft. Why?
You begin to glimpse the idea. It is not necessary to go farther with this boat illustration, save to mark one other fact, which is of vital consequence in our discussion. The difference in lines, of various types of boats, becomes of more and more consequence as the speed increases. No power that could be put aboard could ever make a scow or a canal boat shoot through the water like a torpedo boat of like displacement. The higher the speed intended, the nicer study must be given to the vessel's proportions. The same rule holds good in the case of projectiles designed to be shot through the air..
.
Is only the point of the projectile to be considered? How about its sides and rear?
A ship intended for high speed would not be built with square stern below the waterline— that would be an absurdity. Now a bullet is entirely immersed in the medium through which it travels, like a submarine boat or an airship. Would any one dream of designing either a submarine or an airship on lines like those of a Krag or Springfield bullet? Manifestly not. The flat base of such a body would offer a heavy drag, even at low speed, and the form would be so ill-balanced as to be unmanageable.
I think that even a novice can now see that the ideal form for a bullet would be something like a spheroid or a circular spindle (something like a motor torpedo), but slightly thicker at the forward end, so as to throw the center of gravity forward. A bullet of such form would "slip through the air" more readily than a spitzer bullet, it would maintain speed much better, it would drift less, would be less influenced by contrary winds, and, having no tendency to tumble butt-foremost, it would require a slower twist, and would need no mantel, thus saving wear, and making the gun easier to clean.”
I presented with this article a sketch of a suggested bullet, rounded at both ends and sloping thence very gradually to the shoulder or bearing surface, the forward part being of enough greater diameter than the rear to afford a square shoulder as positive gas check, the bearing here being slightly above true caliber of barrel to bottom of grooves. A sabot, or cup-wad was shown therewith, but I said that whether it would be useful or not would have to be determined by experiment. I doubted it.
This was the first time, to my knowledge, that such an argument was advanced in a sportsman's journal. It passed with little comment at the time; but much has been published on the subject of "boat-tailed" bullets within the past four or five years, especially since it was learned that Switzerland, then France, and afterward other nations, had quietly adopted such projectiles.
On June 8, 1918, Mr. E. Newitt published in Arms and the Man a description of the French balle D '05, with illustration drawn to scale, and ballistic data. He had tested it three and a half years earlier, in Remington rifles made to shoot the French cartridge.
"I was astonished," he said, "by its accuracy and indifference to the strong winds which prevailed during the shooting, and still more by the remarkable flight qualities indicated by the low angle of elevation required. At 1,000 yards the wind allowance was barely half that required by the Springfield, while the hitting of the 36-inch bull's eye seemed to be absurdly easy. A rifle bullet that can give the 1906 Springfield 360 foot-seconds start, overtake it at 500 yards, and beat it in every quality that constitutes excellence in a small-arm projectile, is certainly deserving of more notice than it has received in this country."
The rifle bore for this French cartridge is of .315 caliber. The bullet is 1.55 inch long. Its point is square for a diameter of .05 inch, thence tapers by a very slow curve backward to the shoulder (nearly an inch back from the point) to its maximum diameter of .3287 inch. The shoulder is square but very shallow. From here to the rear the bullet tapers backward to a diameter of .272 inch, with flat base.
The balle D '05 is made in one piece "of an exceedingly hard, tough composition of copper and zinc, much harder and stronger than the lead and cupro-nickel combination [of our bullets]; hence it is less liable to distortion in the barrel or upon impact, and its penetration and destructive capabilities are correspondingly greater." The bullet weighs 198 grains, which is 48 grains heavier than the Springfield, though the entire cartridge weighs only 23 grains more.
Ballistic data, as compared with the Springfield, are given by Mr. Newitt as follows:—
The balle D '05 has a ballistic coefficient, according to Mr. Newitt's computation, of .57. That of the Springfield is .389. This factor, commonly called C, measures the ability of the projectile to overcome the resistance of the air. The higher value of C in the French bullet is due chiefly to the tapered rear and the better distribution of mass (throwing more of the weight forward).
In the latter days of the war we learned that the fighting nations were using projectiles for artillery and small arms that had tapered bases. Although in most instances the tapered part was short, and the flat end of butt was large, yet a decided increase in range was attained, as compared with old-fashioned projectiles of similar initial velocity. The balle D '05 has a longer rear taper than most of them, but still it is far from having a true streamline shape. It is only an approximation toward the ideal form of projectile.
In November and December, 1918, when the censorship had been relaxed, Dr. J. R. Bevis, joint-author of Bevis and Donovan's book "The Modern Rifle," published in Arms and the Man a series of three articles entitled "The Tale of the Tail of a Bullet." Here, for the first time, was demonstrated mathematically the superiority of projectiles tapered at both ends, and a formula was worked out for computing their ballistic coefficients.
Doctor Bevis had already proved that the best form of head for a bullet was not conical, ogival, nor even paraboloidal, but one which is not a continuous curve in outline, and which he calls the para-ogival, head, which, in a bullet of same length as the Springfield's increases the value of C from .389 to .429, and reduces the height of the 1,000yard trajectory approximately two feet, with same muzzle velocity.
I do not know what progress has been made in actual tests of this bullet. Perhaps some difficulty may be experienced from tipping or gas leakage with early patterns, but I can see no reason why this should not be obviated. If the forward part of the bearing is made of bore diameter, so as to ride on top of the lands and insure its axis being in line with the axis of the bore before firing, and back of this the shoulder is of full groove diameter, or a bit more, to form a positive gas-check, as in the Pope target bullets, the edge of the shoulder being square with the longitudinal axis, the bullet should start true and emerge true to the line of fire. Probably no sabot will be needed.
Having reached the limit of efficiency in design of head, he now turned his attention to the tail of the projectile. By mathematical calculation he found that if the Springfield bullet were made with a pointed tail, which would eliminate the vacuum in a flat-based bullet's wake, its 1,000-yard trajectory would be reduced from 14.5 feet to 6.97 feet.
He showed, further, that the bullet's tail should taper not in a curve but in a straight line; and that the cylindrical or bearing part of the bullet should end abruptly with a square shoulder, as true as it is possible to make it, so that as the bullet leaves the muzzle the bearing against the walls of the bore shall cease at the same instant on all sides. The shoulder would also form a gas check. Its depth should not vary greatly from the depth of the rifling groove. He showed that the tail should be as short as would serve the purpose, with maximum angle of taper, and pointed, or as nearly so as practicable.
In the Doctor's own words: "The value of C for any bullet having any shaped head may be increased one hundred per cent by means of its tail. The .30-220 [Krag bullet] with its round nose may be made to have better ballistic properties than the .30-150 Springfield, if the tail is made the proper shape.
"Of two bullets having the same shaped head, and driven by equal charges of the same powder, that bullet having the tail has many advantages over the other. First, on account of its greater value of C, and its having a greater muzzle velocity due to less friction with the walls of the bore, and the greater density of loading, it has considerably greater range for the same elevation of sights, and a flatter trajectory over all ranges.
"Second, for the same causes, the boat-tailed bullet has greater striking energy and greater striking velocity. Its center of gravity is nearer the head, by virtue of which there is every evidence of its superiority in accuracy." He also demonstrated that the boat-tailed bullet drifts less in its flight than one with a flat base.
In a later article, Dr. Bevis showed that it was far better worth while to improve what I have called the "lines" of a bullet than to push its muzzle velocity much farther than our present military cartridges give. "Better ballistics—so much better that a comparison of the two is almost unbelievable—may be more easily attained by increasing C than by increasing the velocity. A bullet of proper construction may have considerably better ballistics at a less muzzle velocity, at a saving of the powder charge, with the same or less pressure, and less friction and consequent less wear upon the wall of the bore of the rifle."
When Dr. Bevis was in the Ordnance Department, during the war, he designed a boat-tail bullet, concerning which I quote the following data, compared with the Springfield.
If the center of gravity is forward of the center of form, it will steady the bullet in flight at all ranges.
Conservative folk may shake their heads in disbelief that this newfangled thing will work as well as it promises. But conservatism often is only a polite name for mental inertia, lack of vision, and plain oldfogy ism. The merits of a torpedo shaped projectile are incontestible, once it has been started straight on its mission, and somebody is bound to devise means of insuring its accurate delivery from the gun.
If we are to have any great increase in ballistic efficiency, with finer accuracy, lower trajectory, longer danger zone, superior energy and shock delivery at point of impact, it must come mainly from better bullets, instead of from speeding up the present type of bullets. With velocities of 2,700 to 3,100 feet a second we already have too much trouble from erosion, metal fouling, melted bullet cores, split jackets, swelled cartridge cases, and other nuisances. A bullet with flat base wastes too much of its energy in fighting the air and keeping from tumbling end over end.
If it pays to follow the streamline form of birds and fishes in designing the bodies of airplanes and racing cars, which meet nothing like the air resistance of a projectile from a gun, and if a dart or an arrow must be heavier at point than at butt of shaft, why should we go on stupidly forcing our bullets to fly wrong end foremost?
All that gun and powder can do is to start the bullet straight, with a certain spin, and at a certain speed. Then and thereafter its accuracy, its maintenance of speed and energy i its penetration and shock delivery, its ability to "jam the wind," depend upon the shape, balance, density, and other qualities of the projectile itself.
If we design a gun and then a cartridge that it is capable of handling, we are going tail-first. The prime problem is the cartridge, and a gun to use it is secondary, to be built according to the requirements of that cartridge. And in getting up a cartridge, the first thing to perfect is the bullet. The missile that is to do the work is the prime consideration.