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myron
Member Posts: 54 ✭✭
can you explain the process for hardening the neck of the cases i cant remember what it is called[V]
Comments
Annealing is a process wherein heat is applied to a metal in order to change it's internal structure in such a way that the metal will become softer.
Most of us think of "heat treating" when we think of applying heat to a metal in order to change it's internal structural properties. The word "heat treating" is most commonly associated with steel. However, the term heat treating is not annealing, except in a general and journalistic sense of the word. Heat treating refers to a process wherein the metal is made harder. Annealing always means to make the metal softer.
In order to make steel harder, it is heated to some temperature, and then cooled fairly rapidly, although this is not always the case. Brass, on the other hand, cannot be made harder by heating it -- ever -- brass is always made softer by heating.
The only way brass can be made harder is to "work" it. That is, the brass must be bent, hammered, shaped or otherwise formed. Once it has been made hard, it can be returned to it's "soft" state by annealing. The hardness of brass can be controlled by annealing for a specified time and temperature.
Unlike steel, which will be made harder when it is cooled rapidly, brass is virtually unaffected when it is rapidly cooled. Annealing brass and suddenly quenching it in water will have no measurable effect on the brass. Cartridge cases are made of brass. When cartridge cases have been reloaded a number of times, the case necks become harder. Annealing will return the cartridge case necks to their factory original state.
Cartridge Case Annealing
"Properly" annealed cartridge cases are essential to maintaining accuracy and long case life when using handloaded ammunition. The question is, what is "properly" annealed? What does annealing do? Can a cartridge case be over annealed? What part of the case should be annealed? Can annealing a cartridge case make it dangerous? Below, you will find the answers to these questions, as well as a number of other questions that you didn't ask.
A great deal has been written about cartridge case annealing in the popular gun press. A great deal of what has been written about annealing is misleading, with one exception: articles and books by Dean A. Grennell. In his "The ABC's of Reloading" (page 190), Mr. Grennell correctly describes the proceedure. Although it is a very short description, it is correct. There is one slight error of fact, but it is on the side of safety and Mr. Grennell cannot be faulted for this in any way. In fact, if you do not have this book I recommend it -- even for "experienced" handloader's. There is much valuable information in it, much of it overlooked in other publications. The photo's are profuse and excellent, the explanation clear and concise, and the writing is witty and wry.
After wading through this weighty tome, you will know more about annealing and cartridge brass than you probably bargained for.
Few handloader's ever bother to anneal their brass. The few that do are usually dyed-in-the-wool "gun cranks" (to use a rather archaic term from the 1940's), "crazy experimenters" or shooters who are involved in some form of competitive shooting. There is good reason for this, too -- until now, annealing cartridge brass was, at best, a spotty proposition. The brass is either over annealed, under annealed, improperly annealed or some combination of all three. Annealing brass is time consuming, and for the most part, the damn stuff doesn't seem to shoot any better than before it was annealed. Sure, the brass lasts longer, but it does not seem to make any improvements in accuracy. If anything, it might seem to open up groups. So much for the way you used to think about annealing.
Now let's find out about doing it right. Not only will annealing make the brass last up to 10 times longer, but it will tighten up those groups too.
Before I go into the why's and whereof of cartridge brass and the right way to anneal, let's review the traditional methods of annealing, the attendant disaster, and how they occur.
The "Old Methods"
The usual procedure is to get a pan, something like a cookie pan, and place enough water water in the bottom of it to cover the lower one-third to one-half of the brass. Next the cartridges are stood on their bases in the water. A flame from a propane torch is played over the case necks until the brass "just begins to glow" or "just before it begins to glow". When the magic moment is reached, the annealing is abruptly arrested by knocking over the heated case into the water. The fact that the case neck is heated unevenly and the case-to-case heating is hardly uniform doesn't seem to get much notice.
The reason for the water is that the bases of the cases must not be annealed, or even heated to any appreciable amount, for reasons you will learn about later on.
Another method is to dip the case mouths into molten lead that is at the "correct temperature. Of coarse, there are the problems of lead sticking to the case (soldering), holding the case, and preventing the base from becoming over heated. This process is obviously one for Superman: he could hold the case with his fingers of steel and freeze the base by blowing his supersonic breath over it.
Quite frankly, I have never seen anyone use the lead pot method of annealing although I have read many articles describing it. I think I can see why it is not a popular method. The next method is described by Earl Naramore in his "Principles and Practices of Loading Ammunition" (circa 1954).
First the cases are polished and then placed on a small block of wood or metal. The case is placed on the platform and a flame from a suitable torch is played over the neck as the block is turned. This continues until the brass has a slight color change, and then the flame is removed. The flame must be hot enough so that the neck is heated sufficiently fast enough to prevent the base from heating to a critical point.
Needless to say, this procedure will work fairly well, but requires a high degree of skill. It is also very S-L-O-W! Can you imagine having to anneal several hundred cases using this method? Another drawback to this method is that you will have a decided lack of uniformity on the periphery of the case neck, and the case-to-case results will be even less uniform. So much for the "old methods".
Cartridge Cases
Our present day cartridge cases represent over one hundred years of continued development and refinement. Cartridge cases are manufactured to exacting standards and tolerances from brass made especially for the purpose.
A cartridge case starts life as a strip of brass. It goes through a number of processes on it's way from brass strip to finished cartridge case. It is punched, heated, cooled, cupped, washed, drawn, annealed, formed, "upset" and trimmed and polished, though not necessarily in that order, and I have left out a significant number of steps. Suffice it to say, the manufacture of cartridge brass is involved and exacting. What we get is truly a marvel of manufacturing magic.
Cartridge brass is annealed several times during the manufacturing process. Each step is carefully controlled, and the brass is tested and examined with sophisticated equipment.
As delivered, a cartridge case has a number of properties especially suited for the job it must perform. Most shooters think of the cartridge case merely as a convenient way of keeping the bullet, primer and powder from getting all mixed up and a handy way of stuffing them all into the gun in the proper sequence. As Rodney Dangerfield might say, "It don't get no respect".
The Cartridge Case Inside The Gun
Actually, a cartridge case is the primary component with which we have to deal in handloading ! Not only that, but it is the cartridge case which seals the chamber when the gun is fired. If it weren't for the amazing ability properties of the cartridge case, you would get a hot blast of gas in your face every time you pulled the trigger.
After the trigger is pulled, the powder is ignited and creates gas pressure inside the case. Under pressure, the case expands. The outer walls of the cartridge case press against the walls of the chamber. As the pressure builds up (as high as 55,000 pounds per square inch or more in a rifle), the outer walls of the case press tighter and tighter. The more pressure, the better the seal (up to a point, of coarse). The primer, held securely at it's outer walls by the same pressure, and pressing against the bolt face (assuming we're still talking about a rifle), does it's part to seal the breach, even though it's primary job is completed by this time.
As the bullet speeds down the bore, the pressure begins to drop. Finally, the bullet clears the muzzle and the pressure abruptly drops to zero (in fact, to atmospheric pressure). The cartridge case, having done it's job to seal the chamber, has more "work" to do. It must spring away from the chamber walls so it may be extracted. If it does not, it will be a bi___ to remove from the gun. . If it fails to spring back from the chamber walls sufficiently, it will seem to be a little "sticky". If it does not spring back at all, it will take the hot hammers of hell to remove it.
In order for the cartridge case to perform it's tricky tasks again and again, it must have it's properties restored from time to time. One of these properties is it's physical dimensions. These are restored each time the case is resized. When a cartridge case is full-length resized, every dimension except the overall case length is restored. Principally, the diameters of the case and the case's shoulder are restored.
Sometimes only the case neck is resized to original factory dimensions. This is due to the fact the cartridge brass has a certain resiliency and is able to spring back to a size which approximates it's original size. It will still fit into the chamber of the gun it was fired in, but it may not fit in another gun, which to all intents and purposes is "identical" in every respect, except that it's chamber may be slightly smaller. As long as the cartridges are used in the same gun after each neck sizing, no trouble will be encountered. Ammunition loaded from brass which has been neck sized only, may group appreciably tighter. I say may, because there are so many variables that only you can determine which is the best combination of components, processes and techniques for your gun.
Each time the case is fired and reloaded, changes occur in it's structure. Except for the obvious changes in dimensions, these changes are not discernable to the "naked-eye". The important changes occur at the molecular level in the brass itself.
Properties of Cartridge Cases
A finished cartridge case is made so that the hardness of the metal varies over it's length. It must be "hard" in some places and "soft" in others. In order to make brass hard, it must be "worked" or, in a crude sense, "hammered".
Most metals "work harden" as they are formed, and brass is no different. The term "work" means that the fine granular structure of the metal is placed under stress and changes as a result of forming or shaping. These stresses remain in the metal in the form of changes to it's grain structure. (This is somewhat oversimplified, but is accurate as far as it goes).
The metallic "grains" can actually be seen if the brass is etched in an acid solution and examined under a microscope with the proper lighting conditions -- obviously a laboratory job, and not a subject which I will take up here. When the grains become too fine, the metal will easily crack. However, there are ways to discern the general condition of the metals structure without a laboratory examination.
The cartridge case, as it comes from the factory, is not one single hardness over it's entire length. The neck, which must hold the bullet in place with sufficient holding power to prevent it's setback while undergoing recoil (as it is stored in a magazine or clip), is somewhat "soft" compared to the head of the case.
By "soft" I do not mean to imply that it is like "dough" or soft like an aluminum beer can. It is "soft" only in comparison to the head of the case. On the other hand, the head of the case is not "hard" like a ball bearing is hard -- it is only "hard" enough to do it's job and no more. If it is too hard or soft, in the wrong places, the cartridge case will fail, and your first indication of this disaster may be a cloud of gun parts flying in into your face. Such a rapid disassembly of a gun is usually attributed to "an overloaded cartridge," but just as well be from a normally loaded cartridge (developing normal pressures) whose case failed rather catastrophically, and, I might add, rather suddenly, because it had lost it's necessary properties.
How hard is "hard", and how "soft" is "soft"? It is not a question which is easily answered, and I will waffle a bit during the explanation. Normally you will use a cartridge case until it is no longer serviceable because of two main reasons: the case necks will become too thin from repeated sizing and trimming operations, or the necks start splitting. In the first case, you will probably detect the thinning by simply looking at the case necks. Your experience will tell you that they are not "right" and that it is time to get a new batch of brass. In the second case, you will spot the split necks as soon as they are extracted from the gun, or possibly during some inspection step during reloading.
If there are only a couple of splits in a batch of brass, you will begin watching it closely (as the neck splits are not particularly dangerous) and occasionally (and unconsciously) touching your wallet as you contemplate the purchase of a new batch of brass.
The reason for the case neck splitting is that the necks have become to hard and are not able to take the expansion and contraction accompanying the rapid pressure excursion which occurs within the case when it is fired.
The thinning of the case necks occurs when the cases are repeatedly resized. Each time the case is run into the sizing die, it is squeezed back to it's original dimensions. That is, the brass is moved from one dimension to a smaller one. You have heard the old adage, "you can't put two pounds of stuff (original word omitted), into a one pound bag". The same holds true here, also. When the case is squeezed, the "extra" brass has to go somewhere. The somewhere that it goes to, is "out the front". The case gets longer. The "extra" brass comes from the body and shoulder of the case -- eventually, the case will "run out of the extra bras". As the case gets too long, it will have to be trimmed. When the necks get too thin, the cases will have to scrapped.
Another thing that happens during the resizing also contributes to the hardening of case necks. As the brass is squeezed back to it's original dimensions, it is work hardened even more. Each trip through the chamber and the resizing die contributes to the work hardening of the case necks. The usual method of correcting this condition is to anneal the case necks only.
Factors Affecting the Annealing Process
You might assume that brass is brass and that a little heat can't possibly hurt anything. After all, the heat in the chamber is actually hot enough to melt steel, isn't it? Yes, it is. But, the "fire" and attendant heat are of such short duration that the brass (including the chamber and barrel) are virtually unaffected. In order to change the grain structure, time (as well as temperature) is an important component. After too much heat or too much time, the brass will be over annealed. It will be too soft, and the entire case will be affected.
The trick is to heat the neck just to the point where the grain structure becomes sufficiently large enough to give the case a springy property, leaving the body changed but little, and the head of the case virtually unchanged.
Brass is an excellent conductor of heat. A flame applied at any point on a case for a short time will cause the rest of the case to heat very quickly. There are several temperatures at which brass is affected. Also, the time the brass remains at a given temperature will have an effect. Brass which has been "work hardened" (sometimes referred to as "cold worked") is unaffected by temperatures up to 482 degrees F regardless of the time it is left at this temperature. Remember, water boils at 212 degrees, and oil heated in a frying pan easily reaches 500 or more degrees. (All temperatures will be in Fahrenheit).
At about 495 degrees F some changes in grain structure begins to occur, although the brass remains about as hard as before -- it would take a laboratory analysis to see the changes that take place at this temperature.
If cases are heated to about 600 degrees F for one hour, they will be thoroughly annealed -- head and body included. That is, they will be ruined. (For a temperature comparison, pure lead melts at 621.3 degrees F).
The critical time and temperature at which the grain structure reforms into something suitable for case necks is 662 degrees F for some 15 minutes. A higher temperature, say from 750 to 800 degrees, will do the same job in a few seconds. If brass is allowed to reach temperatures higher than this (regardless of the time), it will be made irretrievably and irrevocably too soft. Brass will begin to glow a faint orange at about 950 degrees F. Even if the heating is stopped at a couple of hundred degrees below this temperature, the damage has been done -- it will be too soft. From this discussion we can see that there are four considerations concerning time and temperature:
1> Due to conduction, the amount of heat necessary to sufficiently anneal the case neck is great enough to ruin the rest of the case.
2> If the case necks are exposed to heat for a sufficient period of time, a lower temperature can be used.
3> The longer the case necks are exposed to heat, the greater the possibility that too much heat will be conducted into the body and head, thereby ruining the cases.
4> The higher the temperature, the less time the case necks will be exposed to heat, and there will be insufficient time for heat to be conducted into the body and head.
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