Elric
Well-Known Member
This article was written by Dr. Walter Guy Hudson, and for that reason alone is worthy of being tattoo'd on your forehead... Well, maybe not that awesome, but he does touch on bullet drift due to air density differences between the top and bottom of the bullet....
Rifles And Bullets
American Rifleman, vol 37, no. 10, December 15, 1904, pages 208-209
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Target shooting as a sport has been more or less sharply divided into match rifle shooting and military rifle shooting. The points in which the match rifle differs from the military are its lighter trigger pull, finer sights, and better finish; and, in addition, various departures from military styles are allowed in the way of special attachments, butt plates, heavier weight of barrel, etc. The match rifle also is developed with accuracy as its chief aim, and accuracy at the particular distance it is to be used; while the military rifle has to be adapted to all ranges, and be strongly built and serviceable under adverse conditions, even if at the expense of some accuracy.
In view of these considerations, it is scarcely to be wondered at that the target rifle, developed with the sole object of shooting from the offhand position at 200 yards, as in vogue by the German-American (Schuetzen) clubs, should differ so much from the long range match and military rifle. The Schuetzen rifle has changed but little in [100? image is almost blank] years, and in its present form is probably as near perfection for its purpose as it is possible to get. Most of the modern Schuetzen rifles still use black powder, and in the finest American makes the bullet is pushed down from the muzzle as in the old muzzleloading rifles. They are extremely accurate, and the shooting is generally done on sheltered ranges; so that this kind of shooting brings the game down to merely one of skillful holding.
On the other hand, the long range match rifle has of late years approached more and more closely to the military, so much so that most of the match rifles now in use in England are merely military rifles fitted with fine target sights. Skill in shooting at the long ranges, whether with military or match rifles, involves not only good holding, but also a knowledge of the effects of disturbing factors such as changes of light, wind, barometric pressure, temperature, etc.
It must not be supposed, however, that Schuetzen rifle shooting is of no value to riflemen who aspire to honors with the military or long range rifle. The Schuetzen rifle has the advantage of using very cheap ammunition, and the shooting is generally done on ranges provided with facilities that insure comfort to the shooter during even the coldest and most disagreeable weather, and it is the best possible training for tine holding. Therefore it is far better for the rifleman who would keep in practice to shoot 50 or 100 shots at 200 yards, say once a week or two weeks during the winter with a Schuetzen rifle, than to abandon the game altogether during cold weather. There are a large number of civilian riflemen who confine themselves almost entirely to this kind of shooting, and who are nevertheless very well posted and skillful riflemen, able to take up other branches of rifle shooting at short notice; and their skill in holding and intimate knowledge of many of the technicalities of the rifle, learned by long and careful practice with their own weapons, certainly put them far in the lead of the novice, no matter what other branches of rifle shooting they adopt.
But it is in long range shooting, undoubtedly, that the rifleman finds the highest development of the sport. And in late years, since the advent of the modern smokeless powder rifle of high power and small caliber, it is gratifying to note, in our American as well as in the British weapons, that the military and match rifle have approached very near to each other. In the old black powder days, the match rifle with its paper-patched bullet, heavy charge of powder, and necessity of cleaning after each shot was a far different weapon than the military rifle. In those days to attempt to shoot 1000 yards with a military rifle would have been considered the height of folly. But now there is little difference in the scores made with match and military rifles at these long ranges. Indeed, our Krag, when a good barrel can be selected and when the drag is removed from the trigger pull, is in the opinion of many expert riflemen fully capable at the mid and long ranges of holding its own against the finest match rifles that can be produced. There are few target sights that afford better aiming than the 1901 model Krag sight, and while it is true that the target sights as a rule are further apart and adapted to the back position, the modern high power rifle seems to shoot so much better from the prone position as to more than compensate for any slight advantage the target sights might thus gain over our military sight. A glance over the records of those long range matches of recent years that have been open to both military and match rifles will show that in 90 per cent of the matches the Krag has come out victorious. Indeed, the remarkable development of accuracy in the American high power rifle with in the past few years has not been due to any particular refinement in the weapon or sights, but solely to the improvement in the bullet and in the more uniform measuring of powder charges.
To deal understandingly with the differences that have taken place in rifles since the adoption of the high power principle, it will be necessary to look a little into the principles governing all rifles. A rifle may be regarded as an implement embodying all the resources of science and art in the effort to throw a projectile far, swiftly, and accurately. The projectile is acted upon by the natural forces precisely as is a stone when thrown from the hand, the differences, due to the higher velocity of the bullet, being in degree and not in kind. The mystery that in the minds of the uninitiated is supposed to attend the flight of a bullet is chiefly due to the fact that the bullet cannot under ordinary circumstances be observed in its flight, and its motion watched, like the stone.
The first thing that may be taken as true of all projectiles, no matter how thrown, is that they fall toward the earth as soon as the support is removed from them, just the same as though they were not projectiles. But even while they are falling, the energy applied is driving them ahead. From this it will be clear that no weapon, however powerful, can drive a bullet so last that it will go in a straight line; it immediately begins to fall, as soon as it leaves the barrel, unless the latter has been directed upward to some extent, in which case, besides its forward motion, it will rise until the upward force also imparted to it has been expended, and then begin to fall according to the well-known law of falling bodies--slowly at first, but faster the further it falls. The flight of a bullet, therefore, is always in a curved line.
It docs not seem as though air would offer much resistance to the passage of a body through it, but anyone who has ridden a bicycle knows that it docs. Moreover, the resistance of the air increases much more than proportionately with the speed of the moving body, for if the speed be doubled, the resistance will be more than quadrupled. The air, therefore, becomes a much more potent factor in retarding the progress of a bullet than of the stone thrown from the hand, even though, weight for weight, the bullet presents less sectional area. The forward motion of the projectile, therefore, will become slower the further it travels, while its falling speed is continually in creasing owing to the laws of gravity; for this reason, the further it goes, the more curved will be its flight, until at last it drops to the ground.
It is evident that the greater weight a bullet has in proportion to its sectional area, the less will be the degree of the resistance opposed to it by the air, other things being equal. An athlete could not throw a cork as far as a boy could a piece of lead of the same size and shape. Therefore the heaviest available material-lead-—is used in the manufacture of the rifle bullets. For the same reason, the modern long bullet maintains its velocity much better than the old round bullet used in the musket and early muzzleloading rifle.
But when a bullet is made longer than its diameter, some means must be taken to insure its flying in the direction of its long axis—-point on. This is the object of the spiral grooves that are cut on the inside of a rifle barrel, for it is found that if the bullet be caused to rotate with sufficient rapidity on its long axis, it will not turn sideways during its flight. The degree of this twist in the rifling is called its pitch. The longer the bullet in proportion to its diameter, the quicker the pitch of the rifling must be; if the bullet is too long for a given pitch of rifling to handle, this will be shown by the bullet going through the target in a sideways or tipping position--in the parlance of the rifleman, it keyholes. It is necessary for the bullet to be kept point on from consideration of accuracy, as well as to maintain its velocity.
When we increase the proportionate length of our bullet and use a quicker twist of rifling, it becomes necessary to harden the bullet by the addition of tin or antimony, so that it will hold on to the rifling and not be blown straight through the barrel without following the grooves-—stripping, riflemen call it. But when we reach a certain point in lengthening the bullet and increasing the pitch of the rifling no alloy of lead is sufficient to give good results. Therefore, in the modern high power rifle, the bullet is made up of a core of lead, with a jacket of very tough metal, generally an alloy of copper and nickel; and the tough jacket holds on to the rifling so well that we are enabled to fire charges of highly explosive compounds behind the bullet, giving nearly double the velocity that it was possible to obtain with the old black powder rifle. The modern high power rifle is, therefore, one which fires a jacketed bullet very long in proportion to its diameter, by means of a charge of smokeless powder several times as strong as black powder, with nearly double the velocity obtained with lead bullets and black powder; and as a result of the long bullet and high and well sustained velocity, the curve described by the bullet is much nearer a straight line—its trajectory is flatter—its penetration greater, and its range longer.
There is another deviation laterally from the straight line shown by a rifle bullet and more pronounced in rifles having a quick twist; this is called drift. It is a lateral movement due to the spin of the bullet on its long axis. As the bullet is constantly falling in its flight, the under surface meets with more air resistance than the upper, and the bullet therefore tends to roll laterally on this denser air; so that a rifle having a right hand direction to its pitch of rifling will cause a bullet to drift to the right, while one with a left hand twist will drift to the left. Correction of this drift needs to be made on the sights of match rifles, but on the military sight of our national arm —the Krag—the correction is made automatically when the elevation is changed.
WALTER G. HUDSON, M. D.
* This article was prepared by Dr. W. G. Hudson at the request of the Publicity Bureau of the National Board for the Promotion of Rifle Practice.
Rifles And Bullets
American Rifleman, vol 37, no. 10, December 15, 1904, pages 208-209
Google Books scanned this, yet no hits...
Target shooting as a sport has been more or less sharply divided into match rifle shooting and military rifle shooting. The points in which the match rifle differs from the military are its lighter trigger pull, finer sights, and better finish; and, in addition, various departures from military styles are allowed in the way of special attachments, butt plates, heavier weight of barrel, etc. The match rifle also is developed with accuracy as its chief aim, and accuracy at the particular distance it is to be used; while the military rifle has to be adapted to all ranges, and be strongly built and serviceable under adverse conditions, even if at the expense of some accuracy.
In view of these considerations, it is scarcely to be wondered at that the target rifle, developed with the sole object of shooting from the offhand position at 200 yards, as in vogue by the German-American (Schuetzen) clubs, should differ so much from the long range match and military rifle. The Schuetzen rifle has changed but little in [100? image is almost blank] years, and in its present form is probably as near perfection for its purpose as it is possible to get. Most of the modern Schuetzen rifles still use black powder, and in the finest American makes the bullet is pushed down from the muzzle as in the old muzzleloading rifles. They are extremely accurate, and the shooting is generally done on sheltered ranges; so that this kind of shooting brings the game down to merely one of skillful holding.
On the other hand, the long range match rifle has of late years approached more and more closely to the military, so much so that most of the match rifles now in use in England are merely military rifles fitted with fine target sights. Skill in shooting at the long ranges, whether with military or match rifles, involves not only good holding, but also a knowledge of the effects of disturbing factors such as changes of light, wind, barometric pressure, temperature, etc.
It must not be supposed, however, that Schuetzen rifle shooting is of no value to riflemen who aspire to honors with the military or long range rifle. The Schuetzen rifle has the advantage of using very cheap ammunition, and the shooting is generally done on ranges provided with facilities that insure comfort to the shooter during even the coldest and most disagreeable weather, and it is the best possible training for tine holding. Therefore it is far better for the rifleman who would keep in practice to shoot 50 or 100 shots at 200 yards, say once a week or two weeks during the winter with a Schuetzen rifle, than to abandon the game altogether during cold weather. There are a large number of civilian riflemen who confine themselves almost entirely to this kind of shooting, and who are nevertheless very well posted and skillful riflemen, able to take up other branches of rifle shooting at short notice; and their skill in holding and intimate knowledge of many of the technicalities of the rifle, learned by long and careful practice with their own weapons, certainly put them far in the lead of the novice, no matter what other branches of rifle shooting they adopt.
But it is in long range shooting, undoubtedly, that the rifleman finds the highest development of the sport. And in late years, since the advent of the modern smokeless powder rifle of high power and small caliber, it is gratifying to note, in our American as well as in the British weapons, that the military and match rifle have approached very near to each other. In the old black powder days, the match rifle with its paper-patched bullet, heavy charge of powder, and necessity of cleaning after each shot was a far different weapon than the military rifle. In those days to attempt to shoot 1000 yards with a military rifle would have been considered the height of folly. But now there is little difference in the scores made with match and military rifles at these long ranges. Indeed, our Krag, when a good barrel can be selected and when the drag is removed from the trigger pull, is in the opinion of many expert riflemen fully capable at the mid and long ranges of holding its own against the finest match rifles that can be produced. There are few target sights that afford better aiming than the 1901 model Krag sight, and while it is true that the target sights as a rule are further apart and adapted to the back position, the modern high power rifle seems to shoot so much better from the prone position as to more than compensate for any slight advantage the target sights might thus gain over our military sight. A glance over the records of those long range matches of recent years that have been open to both military and match rifles will show that in 90 per cent of the matches the Krag has come out victorious. Indeed, the remarkable development of accuracy in the American high power rifle with in the past few years has not been due to any particular refinement in the weapon or sights, but solely to the improvement in the bullet and in the more uniform measuring of powder charges.
To deal understandingly with the differences that have taken place in rifles since the adoption of the high power principle, it will be necessary to look a little into the principles governing all rifles. A rifle may be regarded as an implement embodying all the resources of science and art in the effort to throw a projectile far, swiftly, and accurately. The projectile is acted upon by the natural forces precisely as is a stone when thrown from the hand, the differences, due to the higher velocity of the bullet, being in degree and not in kind. The mystery that in the minds of the uninitiated is supposed to attend the flight of a bullet is chiefly due to the fact that the bullet cannot under ordinary circumstances be observed in its flight, and its motion watched, like the stone.
The first thing that may be taken as true of all projectiles, no matter how thrown, is that they fall toward the earth as soon as the support is removed from them, just the same as though they were not projectiles. But even while they are falling, the energy applied is driving them ahead. From this it will be clear that no weapon, however powerful, can drive a bullet so last that it will go in a straight line; it immediately begins to fall, as soon as it leaves the barrel, unless the latter has been directed upward to some extent, in which case, besides its forward motion, it will rise until the upward force also imparted to it has been expended, and then begin to fall according to the well-known law of falling bodies--slowly at first, but faster the further it falls. The flight of a bullet, therefore, is always in a curved line.
It docs not seem as though air would offer much resistance to the passage of a body through it, but anyone who has ridden a bicycle knows that it docs. Moreover, the resistance of the air increases much more than proportionately with the speed of the moving body, for if the speed be doubled, the resistance will be more than quadrupled. The air, therefore, becomes a much more potent factor in retarding the progress of a bullet than of the stone thrown from the hand, even though, weight for weight, the bullet presents less sectional area. The forward motion of the projectile, therefore, will become slower the further it travels, while its falling speed is continually in creasing owing to the laws of gravity; for this reason, the further it goes, the more curved will be its flight, until at last it drops to the ground.
It is evident that the greater weight a bullet has in proportion to its sectional area, the less will be the degree of the resistance opposed to it by the air, other things being equal. An athlete could not throw a cork as far as a boy could a piece of lead of the same size and shape. Therefore the heaviest available material-lead-—is used in the manufacture of the rifle bullets. For the same reason, the modern long bullet maintains its velocity much better than the old round bullet used in the musket and early muzzleloading rifle.
But when a bullet is made longer than its diameter, some means must be taken to insure its flying in the direction of its long axis—-point on. This is the object of the spiral grooves that are cut on the inside of a rifle barrel, for it is found that if the bullet be caused to rotate with sufficient rapidity on its long axis, it will not turn sideways during its flight. The degree of this twist in the rifling is called its pitch. The longer the bullet in proportion to its diameter, the quicker the pitch of the rifling must be; if the bullet is too long for a given pitch of rifling to handle, this will be shown by the bullet going through the target in a sideways or tipping position--in the parlance of the rifleman, it keyholes. It is necessary for the bullet to be kept point on from consideration of accuracy, as well as to maintain its velocity.
When we increase the proportionate length of our bullet and use a quicker twist of rifling, it becomes necessary to harden the bullet by the addition of tin or antimony, so that it will hold on to the rifling and not be blown straight through the barrel without following the grooves-—stripping, riflemen call it. But when we reach a certain point in lengthening the bullet and increasing the pitch of the rifling no alloy of lead is sufficient to give good results. Therefore, in the modern high power rifle, the bullet is made up of a core of lead, with a jacket of very tough metal, generally an alloy of copper and nickel; and the tough jacket holds on to the rifling so well that we are enabled to fire charges of highly explosive compounds behind the bullet, giving nearly double the velocity that it was possible to obtain with the old black powder rifle. The modern high power rifle is, therefore, one which fires a jacketed bullet very long in proportion to its diameter, by means of a charge of smokeless powder several times as strong as black powder, with nearly double the velocity obtained with lead bullets and black powder; and as a result of the long bullet and high and well sustained velocity, the curve described by the bullet is much nearer a straight line—its trajectory is flatter—its penetration greater, and its range longer.
There is another deviation laterally from the straight line shown by a rifle bullet and more pronounced in rifles having a quick twist; this is called drift. It is a lateral movement due to the spin of the bullet on its long axis. As the bullet is constantly falling in its flight, the under surface meets with more air resistance than the upper, and the bullet therefore tends to roll laterally on this denser air; so that a rifle having a right hand direction to its pitch of rifling will cause a bullet to drift to the right, while one with a left hand twist will drift to the left. Correction of this drift needs to be made on the sights of match rifles, but on the military sight of our national arm —the Krag—the correction is made automatically when the elevation is changed.
WALTER G. HUDSON, M. D.
* This article was prepared by Dr. W. G. Hudson at the request of the Publicity Bureau of the National Board for the Promotion of Rifle Practice.