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From Ingot to Target: A Cast Bullet Guide for Handgunners©
Alloy Selection and Metallurgy
Lead was one of the first metals that Man learned to purify and manipulate. There are lead figurines still in existence that date back to 3800 BC. Ancient Phoenician trade in lead is described in Ezekiel, XXVII, 12. The ancient Greeks, Romans and Hebrews also mined and worked lead long before the birth of Christ. It has been used for millenia, in a wide variety of applications. Lead-based plumbing (from the Latin name “plumbium” and hence its chemical symbol “Pb”) and lead containing pewter goblets and wine casks were thought to be one of the primary reasons for the downfall of ancient Rome. Lead-based solders made the graceful beauty of medieval stained glass windows possible. Chronic lead poisoning is now known to have killed the musical genius Ludwig von Beethoven (although the source of lead is still a mystery). The United States continues to be a leading producer of lead and it has been mined here since 1621, when the first North American lead mine and smelter were opened near Falling Creek, Virginia. Lead has played a central role in human history.
Lead has been the principle ingredient of bullets for centuries, and its choice for this application is logical: it is dense, easily formed, and widely available. Back when projectiles were patched round balls, it wasn’t necessary to alloy it with anything to make it harder, or to get it cast well, because the surface tension of the molten lead made it “want” to go to a sphere anyway. But when bullets started taking on convoluted shapes and started getting stuffed into cartridge cases, then the limitations of pure lead surfaced. In order to get the molten alloy to properly fill out the ridges and grooves of the mould cavity it was necessary to add something to the lead to lower the surface tension. In addition, breech-loading cartridge rifles had arrived on the scene, and brought with them higher velocities that required harder bullets. Initially the answer to both of these problems was found in the addition of small amounts of other metals (e.g. tin) to harden the alloy moderately. To form a simple substitutional alloy, it is necessary that the added metal have a similar atomic size and electronegativity to the primary metal. Tin satisfies these requirements, mixes with lead very easily, significantly improves castability by lowering both viscosity and surface tension, and hardens the alloy moderately well. Everything was rosy, but then those confounded chemists started playing with nitrate esters of various organic materials and suddenly smokeless powder made its somewhat awkward, but spectacular entry. These new developments meant that much higher pressures and velocities were now possible. The cast bullet would need to get harder.
Cast bullets have always been a natural fit for handguns. But keep in mind that the American handgunner of the first quarter of the 20th century was working with loads at less than 1000 fps for the most part. The .38 Colt Automatic and the .38-40 were the hot-rods of the day at roughly 1100 fps (the exception being the .30 Mauser, but there weren’t that many in the US during this time, and the .38 Super wouldn’t appear until 1929). Men like Phil Sharpe, Major Wesson and Elmer Keith experimented with high pressure loads in some of the stronger guns of the day, but the .357 Magnum wasn’t to see the light of day until 1935, and the .44 Magnum had to wait until 1956 to make its appearance. The handloading handgunner of the first quarter of the 20th century was, for the most part, loading cast bullets at about 850 fps. The modest binary alloys of the black powder era (e.g. 20:1 to 30:1 range) were entirely adequate for this ballistic regime.
Three things happened, slower pistol powders were developed (2400 came out in 1933), magnum revolver cartridges were invented, and tin got to be progressively more and more expensive. It was found that magnum handguns could be made to shoot well with cast bullets IF they were sufficiently hard (“hard” in this case being somewhere in the 10:1 to 16:1 range, with a Brinnel Hardness Number, or BHN, of 11 to 12). One of the cast bullet’s desirable attributes is affordability, but if you’re dumping a full pound of tin into every 10 pound pot of bullet metal, it can get expensive fast! Thus other solutions were sought for hardening bullet metal.
Metallurgy of the Cast Bullet
Lead-tin (Pb-Sn). Which metals do we add to lead to make better bullet metal and why? The first and most obvious need here is to make the alloy harder, but there are other factors that play into this answer as well. Historically, tin was used because it was readily available in pure form, mixed easily with molten lead and contributed desirable properties to both the molten and solidified alloy (castability and hardness, respectively). Tin also increases the hardness of the alloy but does not interfere with the malleability of lead (a key point that we‘ll return to). Tin lowers the viscosity and surface tension of the molten alloy, allowing it to fill out the mould more effectively, resulting in a higher quality bullet. Tin is limited in its ability to harden lead, achieving a maximum hardness of about 16 BHN at 40% tin. These binary lead-tin alloys undergo slight to moderate age softening upon storage (1-2 BHN units), with the harder alloys undergoing more of a change than the softer alloys. The hardness of a binary lead-tin alloy generally stabilizes after about 2-3 weeks. Heat treating binary lead-tin alloys does not provide any change in hardness. At typical lead pot temperatures, lead and tin are infinitely miscible with one another, at the eutectic temperature (361 F) tin is still soluble to the tune of 19%, but at room temperature tin is still soluble in lead at the 2% level, meaning that as the bullet cools down there is significant precipitation of a tin-rich solid solution in the form of granules and needles in a matrix of lead-rich solid solution.
It is important to recognize that tin is well-mixed in the matrix and it hardens lead by making the matrix itself harder.
Lead-antimony (Pb-Sb). Antimony on the other hand hardens lead alloys much more efficiently, with only 1% antimony producing a BHN of 10 while it takes 5% tin to do the same, and it takes only 8% antimony to achieve a BHN of 16, as compared to 40% tin. The name “antimonial lead” refers to binary lead alloys with 1-6% antimony, with the higher antimony alloys (i.e. those with >1% antimony) commonly being called “hard lead” in industry. While antimony increases the hardness of lead, it does so by impairing its malleability. At typical lead-pot temperatures (ca. 700 F), antimony is only moderately soluble in lead alloys, and as the temperature drops, the solubility of antimony is markedly lower than that of tin. At the eutectic temperature for a binary lead-antimony alloy (484 F), only 3.5% antimony is soluble (note that this is 123 F hotter than of the tin eutectic temperature, but the antimony solubility is less than 1/5 that of tin). At room temperature the equilibrium solubility of antimony in lead is only 0.44%. The precipitated antimony appears as small rods, at the grain boundaries and within the grains themselves. Electron micrographs of lead-antimony alloys clearly show discrete particles of antimony surrounded by a matrix of lead-rich solid solution. In contrast to lead-tin alloys, lead-antimony alloys age harden, sometimes as much as 50% or more. When these alloys are air-cooled, some antimony is retained in the lead-rich matrix, and as a result these alloys age-harden as this antimony continues to slowly precipitate. This usually takes 10-20 days to achieve full effect.
It is important to recognize the antimony hardens lead alloys by a fundamentally different mechanism than does tin. Antimony hardens the alloy by precipitation of a separate crystalline antimony phase, which reinforces the squishy plastic lead phase that’s in between the hard antimony crystals. These alloys tend to be brittle because the plastic (squishy) lead phase gets its hardness from the reinforcing hard antimony rods. As the matrix gets deformed the brittle antimony rods shear off and the soft metal fails. In the case of the lead-tin alloys, the tin is more uniformly distributed through out the matrix, making the matrix itself harder, so plastic deformation of the alloy is more uniform and progressive, not the slip/shear of lead-antimony alloys.
Multi-component alloys. Tin still improves castability by lowering viscosity and surface tension. Antimony hardens the alloy via precipitation. The tin also helps to alleviate brittleness by combining with the antimony to form an intermetallic adduct thereby improving the solubility, maintaining the hardness. Antimony also helps to reduce shrinkage as the alloy cools. The harder the alloy, the less it shrinks (lead shrinks 1.13%, linotype shrinks 0.65%). In molten lead alloys, tin and antimony react with one another to form an intermetallic compound (shorthand is “SbSn” to show the adduct between antimony, Sb, and tin, Sn). This does a number of things. First of all, SbSn is more soluble in lead than is Sb. In addition, both free Sb and Sn are soluble in SbSn, as is Pb, meaning that the formation of this phase serves to enhance the mixing of the alloy and limit phase segregation and precipitation. When Sb and Sn are present in roughly equal amounts, the alloy behaves as though it’s a pseudobinary system of SbSn in Pb. Electron micrographs of 94% Pb, 3% Sb and 3% Sn (an excellent bullet metal, very similar to WW alloys with 2% added tin) shows globular grains of lead rich solid solution, with an interdendritic pseudobinary eutectic of SnSb phase (for example see: the Metals Handbook: Volume 7, Atlas of Microstructutres of Industrial Alloys, page 304). Similar electron micrographs of linotype alloys show very thin dendrites of lead-rich solid solution, surrounded by a matrix of SnSb intermetallic phase, with much precipitated antimony rich solid solution (this precipitated phase is why linotype bullets are so brittle and tend to shear upon impact).
How these alloys are hardened depends on the composition. The malleability of lead-tin-antimony tertiary alloys depend heavily on composition, particularly on the tin/antimony ratio. When the concentrations of tin and antimony are equal, the alloy behaves as though it’s a binary system with “SnSb” as the diluent in the lead matrix. The phase behavior of SnSb is notably different than that of Sb -- both in terms of solubility and in terms of crystal morphology. Sb is highly crystalline and only soluble in Pb to the tune of 0.44% at room temperature. SnSb appears to be significantly more soluble in Pb and based on electron micrographs of chemically etched samples, significantly more amorphous. As mentioned before, the SnSb phase serves as a mixing agent, serving to help dissolve excess Sb (or Sn for that matter), and having greater solubility in the Pb matrix. This enhanced mixing, along with the reduced crystallinity means that the lead alloys with a 1:1 ratio of tin to antimony behave somewhat like simple binary lead-tin alloys, only harder (this is why Lyman #2 is 90% Pb, 5% Sb, 5% Sn). Hold this thought…
As the concentration of antimony increases over that of tin, at first the SnSb phase serves to dissolve the small amount of excess Sb. At higher Sb concentrations however the SnSb phase becomes saturated and a separate antimony phase begins to precipitate. At this point, the alloy begins to take on some of the brittleness properties of the binary lead-antimony alloys. As the antimony concentration increases, this brittleness becomes more pronounced. So those tertiary alloys which have 2 or 3 times as much antimony as tin (e.g. linotype, 12% Sb, 4% Sn) tend to be more brittle than those alloys of similar hardness with similar Sb and Sn levels. OK, here’s a subtle point, WW alloy (3% antimony, 0.3% tin) can fall prey to this issue as well, although not as severely since its not as hard. But by adding tin and making the alloy slightly harder, the alloy also becomes less brittle and more malleable due to the formation of SnSb and the elimination of the precipitated Sb phase. Thus, WW alloy with approximately 2% added tin makes an excellent bullet metal with hardness suitable for a variety of applications, and it still can be made harder through heat treating or water quenching. This can also be made using Lyman #2 mixed with an equal amount of pure lead.
In “Cast Bullets” by E. H. Harrison (NRA Publications) WW alloy +2% tin is listed as giving very good castability and a BHN of 13.6. My own measurements run more like a BHN of 11-12 (undoubtedly due to the variation in WW content), but this alloys does indeed cast very well. Recovered range scrap varies from range to range, depending on the nature of the shooting at that particular locale, but it commonly runs fairly soft (in the BHN range of 8 or so) as a result of all the .22 Long Rifle and swaged .38 wadcutter ammo deposited in with the jacketed and hardcast bullets.
Age hardening of the tertiary alloys is more pronounced in the softer alloys, suggesting that at the higher antimony concentrations precipitation occurs more readily during the cooling process. This age hardening can be accelerated by increasing the aging temperature. In general, measuring bullet hardness 24-48 hours after casting provides the most useful, and timely, information.
In addition, arsenic (As) is commonly added to industrial lead-tin-antimony alloys to improve the strength (this strength enhancement is only observed when As is added to a Sb containing alloy, As is virtually worthless in the absence of Sb). Arsenic also significantly enhances the ability of the alloy to be hardened via heat treatment. All that is needed is 0.1% (more does no good). Wheelweight alloy commonly contains about 0.17% As.
Heat treating and water quenching. This age hardening of antimony containing alloys can be accelerated at higher temperatures, i.e. heat treating the bullets. This is most commonly done by sizing the bullets first (since lead alloys work soften, and hence sizing would negate a significant portion of the hardness imparted by the heat treating process) then heating them to about 450° F in the oven and quenching by dumping them in cold water. The hardened bullets are then lubed using the same sizing die that was used before (so that no actual sizing takes place). Done in this manner, bullets cast with an alloy containing 5% antimony, 0.5% tin and 0.17% arsenic, which would normally have a Brinnell hardness of a little over 16 (after aging for 6 days), can be hardened to a BHN of over 35 (see Dennis Marshall‘s chapter “Stronger Bullets with Less Alloying“ in “Cast Bullets” published by the NRA). Notice that this alloy is not tremendously different from the common wheelweight. Much the same sort of result can be obtained by casting with a hot mould and water quenching directly (place a towel over the water bucket with a 4“ slot cut in it to contain the splashes). Mould temperature is critical for maximum effective hardness. Bullets water quenched from a “cool” mould (i.e. one from which the bullets were smooth and shiny) were found to be similar to air-cooled bullets. But bullets dropped from a mould that was “hot” (i.e. hot enough that the bullets were frosty over their entire surface) were found to have BHN of over 30 when water quenched. In a separate study, such a mould was found to have temperature of 430° F, very similar to the optimum oven temperature found in the heat treatment study (ca. 450° F). I don’t normally cast quite this hot, but even so, water-quenching WW alloy routinely gives me bullets with a Brinnell hardness of 18. One of the advantages of hardening bullets in this manner, as opposed to using linotype to make them hard, is that they are tougher and not as likely to shear or fragment on impact.
Why are we so worried about hardness?
In the old days, there was a lot of talk about bullet hardness, and how soft bullets could cause leading by having the bullet metal getting scraped off as the overly soft bullet traversed the bore. But keep in mind, in the old days, they considered a pure lead bullet “soft” (with a BHN of 5) and a 16-to-1 bullet “hard” (with a hardness of 12 BHN). We cast with harder alloys today, and what is considered “hard” and “soft” today is very, very different than in pre-WWII America. The problem is, the Oldtimers spoke in terms of “hard” and “soft“, not in terms of measured hardness values, so a new caster going back and reviewing the older casting literature is easily confused about what causes leading (addressed in detail in a later chapter). Commercial casters almost universally exploit this confusion and use it as a part of their sales pitch, touting their hard-cast bullets (commonly with a BHN of 18-22 ) as being the perfect remedy to prevent leading. T’ain’t necessarily so, Compadre. Extra hard alloys can actually cause leading (again, see the chapter on leading for a detailed explanation of this). The bottom-line is if you’re casting bullets for typical revolvers (standard and magnum, ignoring rounds like the 454 Casull, which is a case unto itself, see chapter on GC bullets), and you are using an alloy with a hardness of at least 11 BHN, any leading you observe is not caused by the alloy being too soft. Remember, Elmer Keith used the Lyman 429421 cast of 16-1 with a BHN of about 11 for the .44 Magnum. What is surprising is that today is all these newcomers that get all hot and lathered worrying over whether their 20 BHN bullets are too soft!?!
Obturation. OK, if we know that soft bullets with a BHN of 6 can cause problems, why don’t we just cast everything out of linotype? If a little hardness is good, then more is obviously better, right? Well, aside from being a really expensive way to make cast bullets, there are some physical drawbacks to this approach. Obturation is the plastic deformation of the bullet metal in response to the applied pressure (from the burning powder). Cast bullet obturation was extensively studied and characterized by Dr. Franklin Mann over a century ago, and summarized in his most excellent treatise The Bullet's Flight from Powder to Target. Using soft cast bullets, he observed bullet swelling from several thousandths of an inch to several calibers, depending on the conditions employed (pressure, barrel condition, etc.). Modern barrels are exceptionally well-made, but there are minor imperfections (one or two ten-thousandths of an inch) in groove diameter, the width of the lands and grooves, minor local variations in twist rate, etc. As the bullet is engraved, these minute imperfections result in an imperfect seal between the bullet and the bore. The defects in this seal will be the same size as the variation in the dimensions. Since the hot gas molecules that are driving the bullet down the bore are less than one ten thousandth this size, gas leakage is a problem. A lot of attention has been paid to groove diameter and hand-lapping or fire-lapping to make this diameter more uniform through the length of the bore. Another issue that is also addressed by such lapping is that of the grooves and lands. If the grooves and lands vary in width, then this seal also is compromised. The forward edge of the land isn’t so much of an issue because the bullet’s forward momentum continuously drives it into this edge, forcing this seal closed. It’s the trailing edge where the seal is compromised if the dimensions vary. This is why it’s not uncommon to see leading “follow the rifling”, the trailing edge seal was compromised and the gas-leak cut the bullet metal at this point and deposited the metal fouling at its point of generation. By matching the bullet hardness to the pressure of the load, we can exploit obturation to prevent this problematic fouling. By reacting to the applied pressure, the bullet metal can undergo plastic deformation to conform itself to the local profile of the barrel, and help to maintain the seal.
It is important to recognize that obturation is not simply an increase in bullet diameter, it is also a backfilling of defects obtained in the engraving process, and therefore plays a role in every shot fired with a cast bullet, even those that are properly (or over-) sized for the bore.
Some folks don‘t like to believe that obturation plays an important role in cast bullet performance. These “naysayers” like to point out that this mechanism only operates at the peak pressure of the load, which only applies to a short period of time and a small stretch of the barrel. This is not true. The models and correlations that experimental ballistician’s have put together to explain the observed behavior generally tend to correlate peak pressure to bullet hardness. This is simply the model that we use to explain the observed data. All metal undergoes some response to applied pressure, the magnitude and speed of that response depend heavily on the hardness of the metal, but lead alloys are soft and the degree of deformation is proportional to the applied pressure. It is important to also note that the rate of gas leakage (and hence gas-cutting) is also a direct function of applied pressure. Thus, peak pressure induces the most and fastest obturation, and enhances the bullet/bore seal when it is needed most, at peak pressure. Lesser pressures at other points along the P vs. T curve induce smaller (and slower) degrees of obturation, that still play a role in maintaining this seal. Obturation is not an on-off switch that only operates at peak pressure, that is simply how the models that have been applied to explain it work.
Obturation is also supported by the sealing effects of the bullet lubricant (see lube chapter). In the absence of obturation, the entire burden of sealing the bullet/bore interface falls on the lube. With a top-notch lube this can be accomplished, but building teamwork between the alloy and the lube is a better way to do things. Is obturation necessary for good cast bullet performance? No. But it IS a tool that we can make use of and make work for us, so why not take advantage of it?
Hardness. So we want to make sure that a bullet isn’t too soft, or leading will result through galling and abrasion, and we want to make sure that it isn’t too hard so we don’t lose the beneficial effects of obturation, and fall prey to leading through gas-cutting. Does that mean that we have to hit a very specific hardness for each cast bullet application? Thankfully, the answer to that question is “No”. Rather, there are a range of hardness's that serve very well for each pressure/velocity level.
The lower end of each of these hardness ranges will expand somewhat in each of these applications. Harder bullets can be used, but they won’t obturate meaning that you’ll have to use a lube capable of sealing the system, since the bullet cannot contribute to this critical job. Hard lubes probably won’t work here. Note the recurrence of BHN 12 in many of these ranges, and remember that’s what the Oldtimers used to think of as a hard bullet. We’ll come back to this thought…
OK, let’s review: antimony hardens lead alloys considerably more effectively than does tin, and costs much less, meaning that you get significantly more hardness for your casting dollar. Where do we get lead-antimony alloys so we don‘t have to use up all of our valuable tin? In the first half of the 20th century, the most common source of lead/antimony/tin alloys was linotype (84% lead, 12% antimony and 4% tin). As this was the age of offset type printing and “spent” linotype could be found virtually anywhere that had a local newspaper. By mixing linotype and pure lead in various ratios, one could obtain bullet metal suitable for widely varying applications. Now that various electronic printing methods have displaced offset type, linotype is becoming increasingly difficult to come by, and relatively expensive. On the bright side however, we have more automobiles in the United States than ever today, and with cars come tires, and with tires come wheelweights (96% lead, 3% antimony, 0.3% tin and roughly 1% “mixed stuff”, some of which is added intentionally, some of which is just junk). The lowly wheelweight has supplanted linotype as the bullet caster’s antimony source of choice -- it is cheap, widely available, easily processed, and makes an excellent foundation for bullet metal.
Wheelweight alloy can be used directly to cast perfectly good bullets, but it has a tendency to be a little difficult to work with if alloy and mould temperatures aren’t ideal. Due to the variation in composition of wheelweight alloy, bullet hardness tends to vary somewhat, but generally comes out in the range of BHN of 10 to 12 for air-cooled bullets. Please note the similarity to the “hard” bullets of yesteryear (10:1 at BHN of 11.5). WW bullets are considered moderately soft today, when in fact they are just as hard, if not harder, than what Elmer Keith, Phil Sharpe or Major Wesson considered “hard”. What’s more, since WW alloy contains not only antimony, but also trace amounts of arsenic, WW bullets can be heat treated for additional hardness. For example, water quenching bullets cast of WW alloy produces a bullet with a BHN of about 18. Heat treating WW bullets can get this number well above 20. Also note that upon the addition of about 2% tin, the bullet metal now becomes very similar to the old electrotype (94% lead, 3% antimony and 3% tin) which casts beautifully, has been reported to age harden to over BHN 16, and can be heat treated to a BHN of well over 20. We are now in the hardness range of linotype (which can cost upwards of $1 a pound), from a metal source that is either free or at most 20% the cost of linotype. In addition, the hardened WW bullets are tougher and not nearly as brittle as the linotype bullets, meaning less likelihood that the bullets will shatter on impact. Extensive field testing by a number of different hunters has borne this out.
At magnum handgun velocities (e.g. 1400 fps), bullets with a BHN of about 12 (e.g. air-cooled WW alloy) will expand somewhat. This is an excellent alloy for deer and black bear sized game. Water quenched WW alloy at BHN 16-18 is quite tough and will neither expand or shatter at these speeds. This is an excellent alloy for maximum penetration. For higher velocity applications (e.g. .357 Maximum, .454 Casull), these harder bullets also commonly provide better accuracy.
So, what alloy do we want for what applications? After experimenting extensively, my choices are:
Standard revolver loads. For this category, a Brinnell hardness of 11 to 12 is desired, so WW alloy + 2% tin is an excellent all-round alloy. It casts well, shoots well and is very versatile. Included in this group are the +P loads (up to about 20,000 psi and 1100 fps).
Standard revolver HP’s. To get a cast HP to expand at velocities below about 1000 fps, it is generally necessary to keep the alloy hardness down to around 8. Traditionally, the preferred alloy for this application was 20:1 lead: tin, which both casts beautifully (if you have that much tin to spare) and expands well at around 1000 fps. Today this level of hardness is more easily achieved using a 1:1 mixture of WW to pure lead, sweetened with a pinch of tin (roughly 1.5% antimony and 1% tin). Field testing at ~1000 fps reveals that this alloy expands just fine (depending on the mould design). Another way to make a similar alloy would be 1 1/4 lbs of linotype and 8 3/4 lbs of pure lead. Remember that Sn hardens lead without any sacrifice in malleability, while Sb increases hardness at the cost of malleability. Thus the linotype approach to this alloy may be somewhat more brittle than the WW recipe, which in turn may be slightly more brittle that the traditional 20-1 (however, brittleness shouldn’t be a major issue since the added tin takes us below the Sb solubility limit, and since these bullets are being shot at only ~1000 fps). In addition, both of the tertiary alloys can age harden which will have a negative effect on HP expansion in this velocity range, so the best alloy is still 20:1.
Magnum revolver loads. The target hardness here is generally something in the range of 12-18 BHN. Achieving this hardness is easy, use the same alloy as described for the standard revolver loads (WW + 2% tin), cast hot and water quench the bullets as they drop from the blocks. According to my LBT hardness tester, these water quenched WW bullets (WQ-WW) has a Brinnell hardness of about 16 and is useful up to about 1700 fps. For loads above 1700 fps, I generally just use linotype (although WW alloy heat treated up to a BHN of over 30 can also be used with excellent results).
Magnum HP loads. Here the target hardness is generally around 12 (depending on the HP design). I use the same thing use for standard revolver loads (WW sweetened with 2% tin), or if I want them a little softer I sometimes use 8 lbs WW alloy + 2 lbs Pb. Either way, they are going to expand at magnum velocities.
Do you note a recurring theme here? WW + 2% tin (or its equivalent) gets used in a lot of my shooting, sometimes air-cooled, sometimes water quenched. The two specialty applications are low velocity HP’s where I turn to 20:1 or 1:1 WW/Pb (or its equivalent), and extremely high velocity, where I use linotype. It’s really pretty simple. I have the raw materials and can custom mix virtually any alloy I want for my cast bullets, but I almost always start with the lowly wheelweight. Why? Because it’s an excellent starting point for a lot of my shooting.
Bullet hardness measurements are an imprecise science, bullets cast from the same pot can, and do, give different hardness values due to the nature of the measurement. In addition, alloys that on the surface appear to be identical can produce bullets with widely different hardnesses based solely on issues like casting technique, mould temperature, pot temperature, and where and how the bullets are dropped. The results you obtain may, or may not, agree exactly with those reported in this chapter as a result of these variables, but the general trends presented here will hold true.
Much of the technical information presented in this chapter was obtained from the following references:
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