Info

a while, as these tin incorporated powders are hard to ignite properly and most of the primers in use at the time they first made their appearance wouldn't do the trick. With proper primers they are excellent powders, but the tin idea was just a little bit late. The ammunition companies had also been working on the problem from the angle of bullet jacket material and about the time the "tin" powders came out, gilding metal jackets also made their debut.

Gilding metal is a high brass composed principally of copper with a small amount of zinc added. It is not new, nor is its use confined to the making of bullet jackets. It 159 varies in composition according to its use and has long been used in the manufacture of cheap jewelry, as one alloy has the appcarancc of gold and does not tarnish easily. The alloy used for bullet jackets is composed of about 90% copper and id°fo zinc. At first, gilding metal jackets were coated with a very thin coating of tin which was applied by a mechanical process. This coating was hardly of measurable thickness and served only to prevent oxidation or discoloration of the gilding metal. The practice of coloring gilding metal jackcts with tin has been discontinued. Western Luba-loy is very similar to gilding metal except that it contains a small percentage of tin in the alloy, which really makes it a bronze. It is to all intents and purposes the same as gilding metal.

(Note. The ammunition made at Frankford Arsenal for the 1921 National Matches had bullets heavily plated with tin. This ammunition was satisfactory when first loaded. Tin has an affinity for brass and in this ammunition the tin combined with the insides of the case necks, forming a union between the bullet and the case just as though the bullets were soldered in place. This union is so strong that it is impossible to extract the bullets and if the ammunition is fired, dangerous pressures will develop. Most of this lot of ammunition, die only one so loaded, has been shot or destroyed, but anyone running across any of it should destroy it or preserve it only as a curiosity in the development of ammunition. It should under no circumstances be fired. The marking on the case heads is, F. A. 21-R.)

Bullet jackets are drawn in much the same manner as cartridge cases. They may be drawn to their finished shape or in the form of cylindrical cups which arc later given the proper form. Great care must be taken to have the jackcts of a uniform degree of hardness, they must be of a proper and uniform weight when trimmed to length and the wall thickness must be uniform all around. If too soft for the cartridge they are made for, the bullets will "slug" excessively when fired. Slugging is a bulging deformation of the bullet that takes place in the barrel when ifo die bullet is too weak to withstand the pressure applied behind it. If the jackets are not of a uniform weight, the finished bullets will also vary in weight and if the wall thickness of the jackets are not uniform, the center of mass of the finished bullets will not coincide with their centers of form. There is no object in going into great detail here on all of the problems of making jacketed bullets, in fact, the only useful purpose to be served by this description is to give the reader some idea of what it is all about so he can appreciate the limitations of the jackctcd bullets he buys, and load them to get the best results. Each cartridge presents its own problems of bullet manufacture and suffice to say that the jacket of a bullet that must expand on animal tissue when fired with a muzzle velocity of 1700 f~s. must be made differendy than the jacket of another bullet of the same weight and caliber that is to be fired at 3000 f.s. Both bullets may loo{ alike but that is probably as far as their similarity will go.

Bullet cores are made of lead alloyed with tin or antimony to give it the proper degree of hardness for the purpose that the bullet is to serve. The cores are swaged to form in the same manner that factory lead bullets are made. As the cores come from the swaging machines, samples are checked for weight, as they must be uniform and of the correct weight if the finished bullets are to be correct. Variations in weight are caused by a lack of uniformity of the percentages of the metals in the alloy. The slugs from which the cores are made may be cast in moulds or cut from wire made of the proper alloy, the latter being the prevalent method today.

To make the lead wire, the metals are alloyed in the proper proportions and are cast in cylindrical ingots. These ingots are put into large hydraulic presses which squeeze the metal through a die of the proper size, extruding it in the form of wire, much in the same manner that tooth paste is squeezed from a tube. Great care is necessary in making the ingots, for when the metal is poured into the 161 ingot mould there is a tendency for the lighter metal in the alloy to rise to the surface, just as it will in a melting pot when casting bullets. This condition will result in one end of the finished wire being of a greater specific gravity than the other. As the shape and volume of the cores is definitely fixed by the dies in which they are formed, the cores from one end of the wire will be much heavier than those from the other end, hence the cores are checked frequendy for weight and when they begin to run lighter or heavier than normal, the balance of the wire is discarded.

The slugs come from the swaging machines covered with oil and all of this oil must be removed from them before they are assembled into the bullet jackets. The presence of oil between the core and the jacket will result in slippage between when the bullet is fired and good accuracy can not be obtained with bullets in which this condition exists. There must be a tight assembly between these two components.

And that brings up a point. Some reloaders attempt to alter the diameters of jacketed bullets by swaging or reducing them in hand dies, so that they will better fit some particular rifle. While this can be done, at least with a fair degree of success, there is danger of ruining the bullets in so doing. The jackets arc of a resilient material while the cores are not, consequently if the bullet is squeezed down to a smaller diameter, die bullet and the core will be compressed together while in the die but when the bullet comes out, the jacket may spring back slighdy, while the core certainly will not. The upsettage that takes place when flat base bullets are fired may off-set this condition, but if it doesn't the accuracy will suffer. Boat-tail bullets do not expand or upset when fired and any attempt to change their diameters by swaging them will destroy their accuracy, especially at the longer ranges.

After the corcs arc freed of oil they are assembled with the jackets, by being forced into them while the jackets r62 are held in dies. If the bullets are of the military or full jacketed type, the cores arc fed into the base ends of the jackets; while for soft point, open point or other expanding bullets having separate tips, they are fed in from the point end. The boat-tail, if any, is then formed and the rear of the jacket based over or the point is formed and the bullets arc passed through a sizing die. Cannelures for crimping, or for weakening the jacket to promote expansion, are rolled in after the bullets are completed otherwise. Canneluring jacketed bullets, and especially boat-tail bullets, tightens the assembly of core and jacket and improves their accuracy. Special care is necessary when making boat-tail bullets without cannelures.

Now for a word about expanding bullets. Way back in the days when grog shops were called saloons instead of taverns there was a caliber .30 rifle called the Krag which tossed a round nose bullet weighing 220 grains with a muzzle velocity of about 2000 Ls. Sporting or hunting bullets for it and other rifles of the same caliber (.30-40) were made with a liberal exposure of lead at the nose of the bullets. These soft point bullets were, at the velocity mentioned, about the best killers of thin skinned game that we have ever had. The soft points mushroomed beautifully, while the high sectional density (length and weight in relation to the area of the cross section) caused them to plow right on deep into the animal after the point had expanded to about twice its original diameter.

But about the same time we were hit with the velocity craze and no rifle or cartridge was any good if it wouldn't shoot as flat as the proverbial pan cake. At increased velocities, the old soft point bullets weren't so good. The noses flattened too quickly and too much, the lead being spread out and separated from the rest of the bullet on impact. This caused bad superficial wounds, while the rest of the bullet with the lead point eliminated often proceeded on its way like a full jacketed bullet, making a deep but small wound lacking in shock effect.

163 The ammunition boys went to work to make new types of bullets that would not expand so easily and that would stand the higher velocities, and they have been at it ever since—trying to make bullets that, at the velocities at which they arc fired, will produce the expansion and deadly effect of the old soft point bullets. Most of these newer bullets have been unsuccessfill; they expand too quickly, destroying too much meat in the smaller animals and opening up or even going to pieces before penetrating into the vitals of the larger ones. There are some very good ones among them and in selecting expanding bullets for loading purposes, the handloader should consider the velocity at which he is going to drive the bullets, as well as the kind of game he is going to use them on. Magazine articles recounting the actual experiences of hunters arc a better guide to selection than ammunition catalogues. It is but natural that the ammunition manufacturers should extole the virtues of their products and sort of forget about their faults; we all do that, but the real reason for recommending magazine articles in preference to catalogues is that the only way that the effect of a bullet on game can be found out is by shooting game with it and that is what the stories tell. Catalogues are inclined to lay emphasis on bullet energy; and frankly, energy expressed in foot pounds doesn't mean a damn thing in a hunting bullet. It is the way that energy is used up on the animal that counts or in other words, the effect actually produced by the bullet.

A large percentage of shooters never hunt or really expect to hunt big game and such hunting as they do is limited to small animals, some of which are very tenacious of life. If the flesh is to be eaten, it is necessarv that as litde as possible of the meat be destroyed by the bullet. For such purpose, full jacketed bullets arc desirable if the average range be long, as these bullets can be driven at higher velocities than cast bullets, but at the shorter ranges cast bullets driven at as low a velocity as is practicable are excellent.

In sctded communities this introduces a complication, as loads of this type are apt to ricochet or glance. The distance that a bullet will ricochet to, or the direction that it will take after impact with the ground or any hard object, is a matter of uncertainty. The heavier the bullet, the higher its velocity and the less it is deformed on impact, the farther it will go when it glances. Cast bullets will usually deform more on impact than jacketed bullets and the more a bullet deforms, the greater the air resistance will be and conse-quendy, the shorter the ricochet range. In artillery firing over water, the ricochet range is considered as being about two thirds of the actual range, but such firing is done at long ranges only, nearly the effective range of the gun, and is an unsafe rule to apply to small arms. If one is shooting at a hundred yards with an arm that has an effective range of 2000 yards, it would be ridiculous to consider the ricochet range as 67 yards. I have known of Springfield bullets causing complaints from about two miles beyond where the bullets struck, so when shooting solid bullets, or any bullets at low velocities, it is well to be very careful of the direction of fire and to only shoot when there is a good back stop for the bullets.

There is another bad feature of ricochet bullets: If they are deformed much on impact, they make a peculiar whining noise as they go through the air and this sound can often be heard for a considerable distance. I have yet to sec an innocent by-standcr who has heard a bullet ricochet that wasn't ready to swear by all that is holy that it went right past his car.

The safest loads to use in a settled community are light weight, open point, jacketed bullets driven at the highest velocity possible with safety. Such loads will almost always cause the bullets to go to pieces on impact; but bullets sometimes behave in a freak manner and very, very rarely one of these light open point bullets will glance. When using them it is still necessary to use care and judgment in shooting, even though the chances of getting a ricochet 165 are remote. These bullets go into such small pieces that the fragments lack the weight or energy to go very far and they offer considerable air resistance in proportion to their size. The trouble with these loads is, that they are ruinous to small game and will practically blow it to pieces. They are excellent for rodents and predatory animals whose meat or fur has no value. What the small game hunter wants is a high velocity load having a flat trajectory, that will kill cleanly without destroying meat, and that will go to pieces on impact with the ground; but it can't be done. Cast bullets, including gas check bullets, can not be driven at very high velocities nor have they particularly fiat trajectories. One can't beat the game by using short, light weight, gas check bullets for such bullets must be driven at lower velocities than the longer ones in order to get good accuracy. They will kill clcanly but they will not break up on impact. Full jackctcd bullets can be fired at high velocities and will kill cleanly as a rule, but they will not break up and will ricochet a long way. The heavier, expanding point bullets can be loaded to give flat trajectories, but most of them will open up more or less, even on small game, and destroy meat, if not the entire animal. Their points will break up on impact with the ground but the body of the bullet will not. For instance, a 150 grain, cal. .30 open point bullet will, on impact with the ground, usually have the point disintegrate but the resultant or remaining slug will weigh about 90 grains, and a 90 grain slug can travel a long way and do a lot of damage. TTie light weight, open point, jacketed bullets can be fired at high velocities and will break up on impact, but they will also break up on and raise the devil with meat. So there you are and take your pick.

There is, of course the question of the hollow point cast bullet but suffice it to say that these can not be driven fast enough to break up with certainty, although they will usually flatten or partially disintegrate to a greater extent than solid bullets, when fired at the higher velocities.

167 PART TWO

Ammunition Assembly

Chapter Five BULLET ALLOYS.

Lead forms the basis of all cast bullet alloys but lead alone is not well suited for making bullets. In the first place, pure lead does not flow well or fill out properly in m a bullet mould and bullets cast of pure lead arc apt to have rounded edges. Furthermore, there is a considerable amount of shrinkage when pure lead cools and, if a bullet mould happens to be small enough to cast a bullet of the correct diameter to use without sizing, a bullet of pure lead from this mould will be found to be somewhat under size. In addition, lead is very soft and bullets cast of it are easily damaged in handling, are likely to be scraped or sheared when being seated in the mouths of cartridge cases, and there is a tcndancy for pure lead to rub off in streaks on the inside of the bore, leading the barrel and rendering it inaccurate. I do not mean to say that lead bullets can not be used, merely that in general bullets of pure lead are more difficult to cast and are less desirable for use than those cast from an alloy of lead and other metals. The metals most commonly used with lead for making bullet alloys are tin and antimony, either or both being used at times.

Tin. Tin is a convenient metal to use in making bullet alloys because of its low freezing point. Tin possesses certain anti-friction properties that slighdy reduce the probability of leading, although care must be taken in using the tin so as to avoid excess in the alloy. As an ¡¿g example of the anti-friction properties of tin, which is commonly used in bearing metals because of this quality, brass (copper and zinc) is almost worthless for bearings; but bronze, (copper and tin) make excellent bearings. The same is true of Babbit metals, as those containing tin are used in high-speed bearings while the so-called lead Babbit can only be used in low speed bearings. The addition of tin to lead hardens the mixture and its hardness will increase as the percentage of tin increases. Lead and tin will form a true alloy, that is, they will mix together when the metal is in a molten state and remain mixed after the metal solidifies. This is known as a solid solution, but lead will only retain about 11% of tin in solid solution. If more than 11 % of tin is used the cxccss tin will crystallize out in the form of pure tin crystals when the metal cools. These crystals will be more or less evenly distributed throughout the alloy. About ioJo of tin, or roughly, a mixture of i part tin to 10 parts lead is about the hardest lead-tin alloy that it is practicable to use for bullets; and this mixture is unnecessarily hard for most purposes. This i to 10 alloy of tin and lead has a further objection in that its melting point is rather low.

The reader should not get the idea that tin, because of its anti-friction properties, is a panacea for leading. It is not I believe, from long and careful observation, that a little tin, judiciously used, will reduce the chances of leading in most arms. On the other hand, I know that too much tin may actually cause leading. Tin and lead form solder and while an alloy containing only io% of tin is hardly comparable with commercial solders, particles of such an alloy will sometimes melt under the heat of powder gasses and adhere firmly to the bore. This is especially true of revolvers, for reasons to be pointed out later.

Antimony. Antimony makes an cxccllcnt hardening agent for bullet alloys, it is used almost entirely as a hardening agent for lead bullets as produced by the ammu-

169 nition companies and, despite the fact that antimony does not have the anti-friction properties of tin, it is nevertheless an excellent hardening agent for bullets when used alone. Antimony will not form a true alloy with lead. The two metals will only remain in solution as long as the alloy is in a molten state; when it cools, the antimony will separate out in the form of antimony crystals distributed throughout the mass of lead, but this is not prejudicial to the casting of good bullets.

Antimony has a certain advantage over tin for alloying bullets in that it is cheaper and need only be used in small percentages and that it will make harder bullets and bullets with a higher melting point than those made from an alloy of tin and lead. The principal objection to its use is its relatively high freezing point (or melting point) which is roughly double that of lead. The presence of antimony in the bullet alloy makes the metal free flowing and permits it to fill out the mould cavity more completely than alloys not containing antimony, as there is a tendancy for antimony alloys to expand slightly on cooling rather than to shrink.

Copper. Copper is of litde use in bullet alloys. Years ago, the Ideal Manufacturing Company of New Haven used to sell a bullet alloy containing copper, they recommended it for use in making gas-check or other bullets which were to be driven at a relatively high velocity; but the fact of the matter is that copper will not alloy with lead and if copper is used in a bullet alloy it will only take the form of more or less irregularly divided particles usually distributed unevenly throughout the mass of lead. These particles of copper will not melt at temperatures which can be obtained on the kitchen range and the fact that the use of this metal has long since been discontinued is sufficient evidence of its faults.

Mercury. Mercury has at times been suggested as a hardening agent for bullets but I cannot urge the reader too strongly to keep away from any attempt to use mercury

170 for this purpose. Properly used, a very small percentage ot mercury will harden lead.

But mercury in the bullet will attack the brass of the neck of the cartridge case and, furthermore, mercury under no circumstances should be applied to molten bullet metal as it will immediately vaporize and the mercury vapor, if inhaled, will prove fatal. There is no remedy for it once it is inhaled. There is a method of gilding brass articles by applying a soft amalgum of gold and mercury to the brass after which the latter is heated and the mercury expelled; but in plants where this is done, extraordinary methods are employed, not only to recover and condcnse the mercury vapor but also to carry off any fumes from it. Where the apparatus is defective or the ventilation insufficient, many deaths have been known to result.

Arscnic. Arsenic is also good for hardening lead, from 1 lA% to 2% giving a satisfactory degree of hardness for all ordinary purposes. The melting point of arscnic varies and is usually higher than that of antimony, although the sublimed product melts at a lower temperature.

This metal is poisonous and begins to volatilize at ioo°C., the volatilization increasing with the temperature. Just what effect the vapors produce on the respiratory system I don't know, but they arc probably injurious.

Both mercury and arsenic have their proper uses in the field of metallurgy but are best left in the hands of those who have the knowledge and facilities to use them properly. Antimony and tin are available almost anywhere, they are satisfactory hardening agents, are safe and convenient to use, and the reader should depend upon them entirely.

Melting Paints.

In casting bullets, particularly bullets that are to be driven at high velocities, the hardness of the bullet is usually the only thing which is taken into consideration but it is well also to bear in mind that the melting points of different alloys are also of importance. The burning temperatures of powder charges, even those developing low 171 pressures, arc grcady in cxcess of the temperatures necessary to melt any lead alloy bullets, the only reason the bullets do not melt is because of the short period of time the bullet is subjected to this intense heat. While the difference between the melting points of different lead alloys is insignificant in comparison with the high burning temperatures of powder chargcs, nevertheless a difference of a few degrees in melting temperature may make the difference between a bullet that is accurate and performs satisfactorily, and one which leads the barrel and is inaccurate.

To better "understand how the melting temperature of bullet alloys is affected by the alloy, there are quite a number of metals whose melting points (or freezing points) arc lowered when other metals are alloyed with them. The terms "freezing point" and "melting point" really mean about the same thing. The freezing point of water is zero C., at which point ice is formed. If the temperature rises at all above this point the ice will melt; this condition holds true of metals and the temperature at which metals solidify is called the freezing point. Obviously their melting point is at about the same place, so for practical purposes the two terms arc interchangeable.

Lead has a melting point of 327.40 C. while tin has a melting point of 232.0°C. But if a small amount of lead is added to a mass of tin, the melting point of the alloy will be lowered below that of the tin: likewise if a small amount of tin is added to a mass of lead, the melting point will be lowered below the melting point of pure lead. Now if we consider the melting point of lead as a point on the side of a square and the melting point of tin as another point on the opposite side of the square, at the proper relative height from the base of the square, and we continue to add lead to the tin side and tin to the lead side, the melting points of the alloys thus formed continue to drop until the two curves formed by the points will meet. This point of junction is known as the "eutectic point." The alloy corresponding to the composition at which the two lines meet is called the "eutectic alloy" and the temperature is the "eutectic temperature." The eutectic alloy is, therefore, the lowest melting alloy in a series.

Perhaps a simpler way of explaining this would be to

are completely melted, drops until the eutectic point is reached after which the melting temperature rises, as more tin is added. When the other end of the curve is reached the lead will have decreased to nothing and the tin increased to 100%, so the melting point will be that of pure tin.

The eutectic alloy of lead and tin is a composition of approximately 63% tin and 37% lead, the melting point of this alloy is approximately i82%°C. The melting point of an alloy composed of 90 Jo lead and 10% tin, which is about the hardest that can be used satisfactorily for bullets, is roughly 228°C. I do not know the exact figures off hand but those given are approximately correct.

The same condition exists with alloys of lead and antimony. If a curve is plotted in the same way with these metals and the freezing points of different alloys measured, the freezing points on the antimony side will become lower as lead is added and on the lead side the temperature will be lowered as antimony is added until the two lines meet.

Was this article helpful?

0 0

Post a comment