The Los Angeles Handgun, Rifle, Air Pistol, Hunter/Field Pistol Silhouette Club

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A collection of comments and articles on the many aspects of bullet casting by various cast bullet shooters
Cast Bullets For Beginner And Expert
SECOND EDITION, 2007 - Joe Brennan
Chapter 4.5 HEAT TREATING LEAD BULLETS

Tom Gray

     Believe it or not, cast lead bullets can be made much harder by heat-treating. Whenever a stronger bullet is needed, heat-treating wheel weights is a way to take the common wheel weight alloy and make it just as hard as the most expensive alloys available to bullet casters.

Why heat-treat bullets?

     For every alloy hardness there is a limit to the speed at which the bullets can be shot. The harder (tougher) they are the faster they can go. In my case, I was shooting in the Cast Bullet Association registered matches at 100 and 200 yards. As such, I wanted to shoot 30 caliber bullets as fast as I could to minimize wind drift. I didn't care about expansion, I just wanted to get the bullet to the target as fast as possible before the wind blew it off course. It's no secret that velocity with cast bullets is limited to the strength of the bullet. To increase the strength, you either have to use an alloy rich in tin and antimony or heat-treat the lead. Rich alloys such as Linotype, Monotype or Foundry type are quite expensive as compared to the commonly available wheel weights. The neat thing about wheel weights is that they are cheap, contain all the alloying elements necessary to be heat treated, and are commonly available. We've mentioned making rifle bullets hard but pistol bullets can also benefit by heat-treating. In some cases, such as with the magnums, wheel weights at a hardness of 11 on the Brinell scale can be made strong enough to take the velocity of say, a 357 or 44 magnum. By simply heat-treating wheel weight bullets they can be made as hard as needed for little or no cost.

Cost?

     Linotype runs around 75 cents to a dollar a pound in my neck of the woods. Higher alloys such as Mono and Foundry type are even more expensive. Wheel weights can be gotten for free or for as little as 15 to 25 cents a pound.

Availability?

     Almost everyone drives a car these days. And when they put new tires on the car, the tire shop saves the old wheel weights. In most cases, if you take your own container down to the shop you buy your tires, they will either give you lots of wheel weights or charge you a nominal fee like 15 to 25 cents a pound. If you're a smooth talker, you can usually get them for free.

Are heat-treated wheel weight bullets as accurate as those made from a richer alloy?

     They most certainly are!!! When I decided to start shooting HT WW's (heat-treated wheel weights) I shot them exclusively for two years in competition. I can tell you from direct experience, that they shot just as well as alloyed bullets and maybe a little better. Why better? When you go to a higher alloy, you are adding tin and antimony. These two alloying elements are both lighter than lead. Thus adding them to make the bullets harder also makes the bullets lighter. When they are lighter, their BC (Ballistic Coefficient) goes down. This means that they lose velocity faster and drift more in the wind than a bullet of the same shape but heavier. Tests that I've conducted showed that HT WW bullets had a BC of about 6% greater than Linotype bullets. When you are shooting in competition, every little bit helps and I won many matches with these bullets.

How do you heat treat bullets?

     There are two ways that are most commonly used. One is to water drop and the other is to do it in an oven.

     Water dropping is done by dropping the bullets right out of the mould into a pail of room temperature water. This method will usually yield bullets with a hardness of 15 to 22 Brinnell. Or, about the same as the Lyman # 2 alloy on up to that of Linotype. The final hardness you will get will be determined by how hot the bullet is when it hits the water. If you cast real hot and fast and your bullets fall from the mould easily, you can get bullets as hard as 22 BHN. If you cast slower and your bullets have time to cool before they hit the water, they will be less hard. In this method, speed and temperature are the critical elements of the process.

     There are a couple of advantages and disadvantages to water dropping as compared to oven hardening.

     On the disadvantage side, they will not get as hard as can be gotten in an oven. Also, there will be a greater spread between your hardest ones and your softest ones in the same population due to bullet temperature changing from one casting to the next. It's hard to keep the same rhythm and to make things worse, the mould may get hotter as you cast causing the last bullets to be harder than the first. To make matters worse, whenever a bullet hangs up in the mould, it will cool off sufficiently to make it considerably softer than its brothers. Nevertheless, very good, medium hard bullets can be made using this method. One other disadvantage is that there is a chance of damaging the bullets as they fall thru the water and impact with the ones in the bottom of the pail.

     On the advantage side, water dropping is relatively simple and easy to do. It doesn't take much time to set up a pail of water and drop bullets into it right from the mould. As long as you aren't pushing the velocity envelope, you will probably never see any difference in performance on target.

How do I water drop?

     Get yourself a 5 or 6-gallon pail and fill it with room temperature water. Colder water is not necessary. Place a towel or sponge on top of the water so that when you drop the bullets onto it, it will interrupt their fall into the water so they don't impact the others in the pail. Make sure it just breaks their fall and doesn't cause much delay of the bullets getting into the water. They should just bounce off, not lie on the sponge. Some enterprising casters have made a set of slanted steps in the pail under the water so that the bullet hits the first one, rolls off onto the second one and then falls slowly to the bottom of the pail with no damage to the bullet banging into the others. In most cases, it you aren't making match grade bullets, you can just put a rag in the bottom to cushion the fall and sort out the ones with dented bases later.

A word of caution.

     Never set the water filled pail in a location where water can splash into the pot of molten lead. Just one small drop is all it takes to blow several pounds of lead all over you and the surrounding area. You could be severely burned or worse yet lose an eye. Always wear a protective face mask or glasses and keep your exposed skin covered with heavy clothing and gloves. Also, make sure that any water that gets on the mould is dried off before bringing the mould anywhere near the pot. The way I do it is to set the pail behind me where I have to turn around to drop the bullets out of the mould. That puts me between the water and the lead pot. This method is relatively safe and doesn't slow you down to any degree. After the bullets have cooled, remove them for inspection and processing. Wait about 12 hours and they should be ready to shoot.

How to oven heat-treat.

     The nice thing about oven treating is that the heat treat process is much better controlled and bullets can be made that are just as hard and tough as those made from a rich alloy. Using this method, I've produced bullets as hard as 32 on the BHN scale and was able to drive them at 2500 feet per second with sub minute of angle accuracy. How's that for performance with a cheap alloy?

The equipment:

     All thatís needed is a common kitchen oven and a sink full of tap water. I've used my wife's oven in the kitchen with very good success. The hardest thing was convincing her that those nasty lead bullets weren't going to hurt her oven and that we weren't going to die of lead poisoning! The trick to getting bullets hard is to get them as hot as possible without causing any damage from slumping or dents from lying against each other. When they are quenched at the hottest temperature they can stand, they will get up to 30 BHN with no sweat. The temperature that is needed to do this is around 450 to 460 degrees F. This temperature is easily reached in the common household oven. One thing to watch is that the oven temperature dial is calibrated. It's not uncommon to find the actual temperature in the oven up to 50 degrees off from what the dial indicates. In my case, I happen to have an industrial digital thermometer that has a probe that I can put in the oven among the bullets. If you don't have such equipment available, don't despair. All you have to do is put a couple of bullets in the oven lying with half their length hanging off in space. Keep increasing the temperature in 10 degree increments in the oven till one of them slumps or the nose breaks off and falls away under it's own weight. Then, after noting that temp on the dial, back it off 10 degrees and try heat-treating some bullets. Remember, for maximum strength, you want to get them as hot as possible without getting them so hot that they slump or get dents from lying against the container or each other. With good temperature control you should be able to approach 460 deg. And get very hard bullets. I would first suggest shooting for 450 degrees till you get the process worked out.

     When I first started heat-treating, I made some simple trays out of wire cloth by bending the sides up to form trays that were approx. 6" by 10" and a half an inch deep. I took some coat hanger wire and made a bail type handle on each end to pick it up with. I've found that I could stack the bullets horizontal in the basket two deep without incurring any damage when they were hot. The sweet thing about this setup is that when quenching in the sink full of water, the water comes up thru the bullets very quickly and uniformly and the bullets will all come out with the same hardness. The hardware cloth, sometimes called "wire cloth" can be purchased at a hardware store. I used the kind with about ľ" squares. Think of the wire they use to use in the bottom of rabbit hutches to let the little balls fall thru!! These things donít have to be expensive or elaborate to work.

     The way I do it is to place about a hundred bullets in each tray and place them in the oven. I've already pre heated the oven to the desired temperature. I then let them heat soak for 45 minutes to make sure that they are heated uniformly all the way through. I usually place some tin foil above and below the bullets to keep the direct radiated heat from the bullets. If direct radiated heat is allowed to hit the bullets, the ones on the top will get hotter than the ones on the bottom and thus you will end up with different hardnessís from one bullet to the next even in the same production lot.

     When they have heat soaked for a sufficient time, (usually 45 minutes), I put on a pair of welder gloves and very quickly open the oven door, grab a tray of bullets and move directly to the sink where they are dunked into the tap temperature water without delay. They should sizzle when they hit the water. At that point in time, I prepare another tray with bullets and put it in the oven.

     The next thing I do is to process the bullets that were just quenched while the next batch is getting hot. The reason I do this is because the bullets take about 12 to 15 hours to get up to full hardness and are still quite soft in the first half hour after the quench. Adding gas checks and sizing/lubing while they are still around 11 BHN makes it a lot easier on you and the equipment. My tests have shown that processing them within the first half hour has no effect on the hardening process. You do them while they are soft and let them get hard later.

The Hardening Process.

     I'm no metallurgist. So I'll leave it up to the experts to explain the technicalities of what is happening to make the bullets get harder. It has to do with grain growth. Whenever a wheel weight bullet is taken up to a certain temperature (let's call it the critical temperature), a process is set in motion inside the bullet alloy that causes it to change and make the bullet harder and tougher. This doesn't happen instantaneously such as with ferrous metals when they are quenched in heat-treating. With WW bullets, it starts as soon as they are quenched and they continue to get harder for the next 12 to 15 hours at room temperature. During that time, "grain growth" is taking place. I know this to be true, as I've tested them every hour after quenching and noted when they reached the peak hardness. There's a lot of information out there that may contradict my data, but that's what I've found to happen with my alloys in my oven.

     Many people are concerned that heat-treated bullets will lose their hardness over time. This is true, but it takes a long time for them to lose enough hardness to make any difference. I've tested my own bullets a year later and they went from maybe 30 BHN to 28 BHN. That's not much and anyone who lets their bullets lie around for a whole year has a personal problem and need to shoot more!

What if I want bullets that are softer than 30 BHN?

     No problem, there are two ways to do this. The first is to soften (draw or anneal) them back to the desired hardness. This is accomplished by placing them in the same oven and heating them for a period of time. The longer they are in there, and or, the hotter the oven, the softer they will get. In other words, this drawing back process is both time and temperature dependent. Again, this takes some experimenting to get the process down so that you get the hardness you are going for. In this case, the bullets don't need to be quenched but can be allowed to air cool back to room temperature.

     The second method is one that I worked out that yields predictable and repeatable results. It has to do with the temperature that you run the oven. Back when I had more free time than I have now, I worked out the process to do this. By figuring out what hardness you want in the end, you have to find the right quench temperature to yield that hardness. I found that up to a certain temperature the bullets just lay there and nothing happens. Then after crossing that (critical?) temperature, they start to get harder and harder as the quench temperature increases. I've included a graph at the end that shows the hardness values that I achieved at different quench temperatures. As you can see, the final hardness can range from 11 BHN 30 BHN. I've got to confess that I never really used it much as I always shot bullets in my benchrest gun that were as hard as I could make them. But, for someone who requires an inexpensive bullet at a certain hardness, (such as 22 BHN to equal linotype) referring to the graph for the right quench temperature is an easy way to get it. Note: this graph was developed using my alloys and I think that it's fair to say that other alloys may yield different results. I suggest you experiment with the process a little to get it adjusted to your own particular alloy.

     Attached is a graph that I developed from the test I conducted by quenching at different temperatures. As you can see, nothing really happens till you reach about 410 degrees and it appears to be a straight-line progression after that. I experimented quite a bit with quenching at 445 degrees and found the results are predictable and repeatable. This yielded a hardness of 26 to 28 BHN, which is what I wanted for my match bullets.

Do I need a special alloy to heat treat?

The answer is NO. Wheel weight alloys contain everything that is necessary to respond to heat treatment. The secret is to have a little arsenic in the alloy. Without that, the process won't work. Fortunately, wheel weights already contain enough arsenic that your heat-treat needs are met. I suggest adding some tin to the wheel weight alloy so as to make them easier to cast. What I do is add from Ĺ% to 1Ĺ% tin by weight to the wheel weight alloy and it makes much nicer castings. It's really worth it and doesn't add much to the cost or detract from the heat-treat-ability of the metal. You want to arrive at about 2% tin content for best casting. Since WW's already have about a half percent tin, you only need to add a maximum of 1 Ĺ% more to reach the ideal 2% level.

     That's about it. Without making this any longer, I think you have enough information to start making your own cheap hard bullets. Remember; the whole process is dependent on temperature and how quickly you get them from the mould or oven into the water.

Bullet Quenching

By Dave Goodrich

     Having just recently joined the CBA and discovering the CBA forum, I was very excited to begin learning about cast bullet shooting on a higher level. I consider myself a knowledgeable caster. I have been casting my own bullets for over 25 years, both as a cost saving measure and as a confirmed muzzleloader. We muzzleloaders just like doing things ourselves, and as a group, we tend to never buy what we can make.

     Joe Brennan had asked the CBA list for a short instruction on bullet quenching, the act of heat treating bullets by dropping them into water directly from the mold when casting. As I have used this method with success for many years and many thousands of bullets I offered to detail my process.

     Bullet quenching, sometimes called water dropping, works well and is very simple. I use a 5 gallon bucket, a metal colander, and an old bath towel. The basic premise is this. You put the colander into the bucket, add water, and start casting. As each bullet is ready to fall from the open mold you hold the mold over the bucket and allow the bullet to fall into the water. Sounds simple enough right? There are a few caveats I have discovered over the years, and here are my solutions.

     Text Box:  
You must be careful to keep water away from the hot mold. I have always used an old bath towel over the bucket with a hole cut into it. The towel should be draped into the bucket so as to allow a gentle slope for the bullet to roll down and into the water. This little water which might splash back up out of the bucket is generally caught by the towel.

     I have also experienced bullets being damaged when they hit the bottom of the bucket or hit other bullets. I use a big enough bucket ( five gallons ) so that I can maintain a water level high enough to slow the bullet down sufficiently to stop any damage. I have found 8 inches of water to work well for me.

     Getting the bullets out of the bucket can be a chore, the smaller the bullet, the worse the chore. I use a metal colander that nearly fills the bucket. This allows the bullets to be removed simply by lifting out the colander.

     Using this simple setup I have cast thousands of 357, 32-20, and 303 British bullets and quenched them without problem. There is one side effect you should know about. The simplicity of bullet quenching comes with a price. Your final BHN can and will vary depending on your casting technique. We all know that consistency is key to good bullet casting. Time in mold, alloy temp, the physical timing of pour-cool-cut-drop all play a part in casting proper bullets. Quenching from the mold will increase any deviation you have in your final BHN.

To show this I cast several hundred bullets for my 357 using Lyman #357446 and then tested them for BHN using the LEE Hardness Tester.

     BHN testing occurred at two weeks after casting. The testing was done with a timer to ensure consistent time under the indent ball of the tester. All bullets were at the same temperature, and all bullets were tested at the same time. Note that there are two things I did to ensure accurate test results. First, I did not read any results until all testing was complete, so as to not influence how I performed the test itself. Second, the LEE tester provides a microscope to read and measure the impression the tester makes into the lead. The act of holding the microscope itself can cause problems. Measurements can vary depending on light angle, movement, and the angle of the microscope.

     To reduce the chance of error, I purchased a metal doll stand from Wal-Mart. After a bit of coaxing, I was able to create a fixture to hold the microscope rock steady and in the same position each time. This I hoped would increase my accuracy, and more importantly, provide a higher measure of repeatability. If you have a LEE tester, I highly recommend this method.

     When casting, the time the bullet is in the mold can vary depending on the size of the sprue, or if the bullet hangs in the mold and requires an extra tap to dislodge it. In addition, bullets that are quenched can be affected by the height of the mold over the water. For that matter, the BHN of the bullets nose could change depending on whether the bullet's nose, or the base, entered the water first.

  BHN BHN   BHN

BHN

Sample # AS CAST QUENCHED Sample # AS CAST

QUENCHED

1 11.0 19.3 16 11.0

19.3

 
2 11.0 24.8 17 11.0

20.9

 
3 10.4 24.8 18 11.0

22.7

 
4 9.8

13.4

19 10.4

20.9

 
5 9.8 22.7 20 10.4

20.9 

 
6 11.0 20.9 21 11.0

24.8

 
7 11.8 20.9 22 11.0

24.9

 
8 10.4 22.7 23 11.8

22.7

 
9 9.8 24.8 24 11.0

13.4

 
10 11.8 20.9 25 11.0

22.7

 
11 10.4 20.9 26 10.4

16.6

 
12 11.8 24.8 27 10.4

22.7

 
13 10.4 24.8 28 10.4

19.3

 
14 11.0 24.8 29 10.4

23.8

 
15 11.0 15.4 30 18.4

22.7

 
     

S.D.

0.56

  3.16

 

     The results of testing show that the BHN can vary greatly. Note that the as cast BHN has a lower SD. While the same variances in casting technique can affect bullets not quenched, the bullets that are allowed to air cool are in effect being annealed and the variances in casting technique are minimalized. When the bullets are water quenched, and variances in casting are literally frozen in time.

     Does this matter? That depends on your requirements. I have never noticed any effect of having my BHN vary from quenching. I still enjoyed 1 in groups from two 357 revolvers at 25 yards. My 32-20 would still hit a ram at 200 meters all day long. I never experienced any leading, so the quenching was working. Your needs and results may vary.

     For me heat treating allowed the use of plain wheel weight metal to be used in max velocity 357 magnum loads in my Colt Lawman with plain based bullets, something I couldn't do without heat treating. I also was able to load my Marlin 32-20 above it's normal potential (note this was a MODERN Marlin 1894CL) with H4227 and shoot all day. Nearly any other bullet metal I experimented with left leading after thirty to forty shots. Using heat treated wheel weight metal I could shoot all day with just about any decent commercial lube and have an easy time cleaning the bore.

     I believe it is safe to say that for general plinking and relaxed target shooting, if the accuracy meets your needs, then why worry. Bullet quenching offers a simple low tech way to increase your alloy hardness with a minimum of fuss and bother.

     "I just read Dave's article on bullet quenching out of the mould. This was well written and the data was nicely presented. Nice job Dave! We need more of this kind of stuff.

     I too have done some experimenting with quenching out of the mould, albeit quite a few years ago. At the time, I was looking for stronger (read that as harder) bullets for magnum pistols and for standard velocity rifle loads using wheel weight alloy. As I recall, my BHN results closely paralleled those that Dave experienced.

     When I discovered that BHN (Brinell Hardness Number) readings were varying all over the place, I decided to investigate the cause and effects. I had purchased and was using an LBT tester of the first type that Veral sold and it seemed to give very repeatable results that agreed with the readings that I should find with pure lead, wheel weights, Linotype and Foundry Type. I had each of these alloys on hand to use for test samples. Once having some confidence in the testing procedure and results, I proceeded to test cast bullets after calibrating the LBT tester on the 4 alloys I mentioned above.

     Just as Dave found, I too found that the average BHN reading from dropping bullets into a bucket of water out of the mould ran an average of 22 BHN. This was sufficient hardness for magnum handgun loads and for rifle loads in the range of 2200 fps. However, the fact that BHNís varied so widely continued to be a concern.

     As a result, the first thing I looked at was the amount of time it took for the bullet to enter the water after casting in the mould. If I had a balky/sticky mould and bullets hung up and failed to fall out right away, I found that those bullets were not as hard as ones that fell right out of the mould into the water immediately.

     The second thing I did was to monitor the temperature of the melted lead in the pot. I found that by weighing each bullet immediately when it was cast and comparing that bullets weight to the temperature of the lead in the pot at the instant it was cast, any change in pot temp. caused a change in the weight of that bullet and it's size. When quenching out of the mould, we know that if the bullet was hotter, it would achieve a higher BHN level given all other variables were held in check. I also found that to control weight variations, I needed to control the pot temperature. Just throwing a cold, one pound ingot into a 20 lb capacity pot made a dramatic difference in the pot temp. and the bullet that was cast from it at that instant.

     I then suspected that mould temperature had something to do with the as-cast size and resultant BHN reading. To study that variable, I attached a thermocouple to the mould blocks themselves and again weighed each bullet as it was cast and compared it to mould temp. at the instant of casting. I attached the thermocouple to the mould by first crimping a spade lug electrical connector to the twisted pair of wires from the unit. I then drilled a hole in the mould where it wouldn't interfere with the cavities and tapped it for a 6-32 screw. I then just screwed the spade lug connector to the mould so as to get a heat transfer to the thermocouple. I wish I could remember the temp. readings I got but it was a long time ago and age related condition called "CRS " has set in. I do recall that the mould temp. was not too far below the melt temp. in the pot.

     What I discovered was that the big variable to bullet weight and the resulting hardness was the effect of mould temp. at the time it was injected with the alloy. As we all know, head pressure also plays a part so I used a ladle with the same amount of lead in the ladle each time. What really caused the biggest variations in mould temp was the casting rhythm, or in other words, how fast you cast and how consistent you keep the time between cycles constant. If I cast faster, bullets became heavier and harder. If I slowed down they weighed less and didn't achieve the same hardness. We are talking weight variations of 1 or 1.5% and hardness variations from maybe 17 BHN to 23 BHN.

     In summary, I think that perfectly usable bullets can be cast using the quench from the mould process as long as certain variables are controlled.

     Having a melting pot that regulates the melt temperature closely really helps. Not dropping cold ingots into the melt helps. One thing I found was that if you pre-melted the lead in another pot and ladled it into the pot you were using from, melt temps. were a lot more consistent. A friend of mine with a commercial bullet making business had casting machines that had two pots. One melted the ingots and the other side was fed pre-melted lead and metered it into the moulds.

     Keeping a consistent rhythm to your casting helps keep the mould temp. consistent. Consistent mould temps. relate directly to consistent weights and consistent hardness after quench.

     Having a mould that is properly tuned so that the bullets fall immediately into the water is very important. If bullets are sticking, stop and fix it before proceeding.

The whole key to producing consistent bullets with this process is maintaining consistency in all the operations and using a good mould. If this is achieved, there is no reason a person cannot produce good quality lead bullets. Tom Gray

Heat Treating Lead Alloys and the Effects on BHN

By Dave Goodrich

     When Joe Brennan first asked the forum for help testing bullets for BHN, I eagerly volunteered. The test itself gave me a reason to purchase a lead hardness tester, something I had put off for many years. I ordered the LEE tester, as I thought it would be the most versatile. The price helped, but was not the determining factor. The test went well, and much was learned. But the results left me with more questions than answers.

     There have been articles on heat treating bullets for many years, in almost every reloading magazine. Joe was curious why so much print was given to heat treating, when so few CBA competitors actually seem to use heat-treated bullets. I volunteered again, offering to test the effects of heat treating on BHN.

The First Test:

     The test I envisioned would involve three alloys; common wheel weights, Lyman #2, and range scrap. Alloys that most casters would have available, and could benefit from heat-treating. Each alloy was used to cast 100 bullets.

     #NOTE - After some discussion with other casters it was decided that the test should be done with only wheel weight alloy. Lyman #2 is not normally used for heat treated bullets and range scrap can vary widely depending on what bullets are used at each range. So while the following tests were done on all three alloys, I will only talk about the results found using wheel weight alloy.

     The bullets were cast in batches, then culled and sorted. Ten bullets were tested in "as cast" condition, 10 bullets were quenched in room temperature water, directly from the mold, and 10 bullets were heat-treated. The process of heat-treating used was a common method. The bullets were heated in a 450 degree oven for 1 hour, then quenched in room temperature water.

     All the bullets were color coded, numbered, sorted, and kept in separate containers, so as to not risk confusion when testing the BHN of each bullet.

     BHN testing occurred at 72 hours after casting, and again at 10 days after casting. The testing was done with a timer to ensure consistent time under the indent ball of the tester. All bullets were at the same temperature, and all bullets were tested at the same time. Note that there are two things I did to ensure accurate test results. First, I did not read any results until all testing was complete, so as to not influence how I performed the test itself. Second, the LEE tester provides a microscope to read and measure the impression the tester makes into the lead. The act of holding the microscope itself can cause problems. Measurements can vary depending on light angle, movement, and the angle of the microscope.

     The results of the test were an eye opener, to say the least, and not at all what I expected. Results showed far too much variation to suit me. This is lead after all. Two pieces of lead from the same pot should have the same BHN, logic dictates it. The results were erratic enough that I threw out two of the tests, starting over, recasting and heat-treating the bullets again. The second test showed the same variances. As a programmer, I know that any result that cannot be duplicated, cannot be trusted. If I have a known process, and I change one variable, I should be able to predict the new result with accuracy. If not, then my process is flawed, or I have a variable that I have not taken into account. I believed in the process, and my test controls were good, so I set out to find the missing variable.

Test One Results
 

As Cast

Quenched

HT

 

As Cast

Quenched

HT

 
Sample #

BHN

BHN

BHN

Sample # BHN

BHN

BHN

 
1 10.10 19.30 27.20 16 10.40 20.00 27.20
2 10.10 13.40 27.20 17 10.70 17.90 27.20
3 10.40 17.90 27.20 18 11.00 16.60 27.20
4 10.70 11.80 27.20 19 10.70 12.50 27.20
5 11.00 14.30 27.20 20 10.70 12.50 27.20
6 10.40 16.60 27.20 21 10.70 12.50 27.20
7 10.40 12.50 27.20 22 11.00 19.30

27.20

8 10.40 14.30 27.20 23 10.40 15.40 27.20
9 10.40 20.00 27.20 24 10.40 14.30 27.20
10 10.70 15.40 27.20 25 10.70 13.40 27.20
11 10.70 11.80 27.20 26 11.00 13.40 27.20
12 11.00 13.40 27.20 27 11.00 20.00 27.20
13 10.70 17.90 27.20 28 11.10 20.00 27.20
14 10.10 19.30 27.20 29 11.00 21.00 27.20
15 10.40 14.30 27.20 30 10.70 13.40 27.20
      (All 30 Tests)

10.56

15.55

27.20

 
Average
     

S.D.

0.31

2.98

0.00

 

     I reviewed the test process several times, looking for any variables I did not attempt to control. Looking at the test results, I began to see a trend. The wheel weight bullets that were quenched had the highest SD, 2.79 BHN. The wheel weight bullets that were heat treated, had an SD of only .09 BHN. I also noted that the only batch that had an SD of 0 were the heat treated wheel weight alloy, when tested after 72 hours. Could the act of casting change the BHN of the resulting bullet?

     When casting, the time the bullet is in the mold can vary depending on the size of the sprue, or if the bullet hangs in the mold and requires an extra tap to dislodge it. In addition, bullets that are quenched can be affected by the height of the mold over the water. For that matter, the BHN of the bullets nose could change depending on whether the bullet's nose, or the base, entered the water first. Too many variables here for my liking.

The Second Test:

     I designed a new test to remove the act of casting from the process. Instead of testing bullets, I would test the ingots directly. I would also file a flat smooth surface onto the ingot, to ensure that I was testing the alloy only, without any remaining effects of the casting process. I determined that I could slant my ingot mold 45 degrees and cast an ingot much like the shape of a house roof, and file off a flat surface suitable for testing. (Note, the instructions that come with the LEE tester also recommend filing the surface before testing).

     All ingots were cast within minutes of each other. The ingot mold was preheated and kept at that temperature while each ingot was poured. Two ingots were poured at the same time. Once cooled, each ingot had the top, or peak of the roof, filed flat to provide a smooth testing surface. Half of the ingots were then "normalized". I put these ingots into a 450 degree oven for 1 hour. They were allowed to cool naturally, in a draft free area. All six ingots were then marked and set aside for 72 hours.

     After 72 hours, each ingot was then tested 5 times, then dated. Next, I heat-treated all of the ingots. They were arranged carefully into a metal colander, so that each ingot shared an equal space. The colander was put into a 450 degree oven for 1 hour, then immediately quenched in room temperature water. The ingots were again set aside for 72 hours, then tested again.

     I now had two ingots. One tested in it's "as cast" condition, and one tested after being normalized. Measuring each test showed a large improvement in BHN consistency! I had found my variable. The SD fell to zero in all tests except, the "as cast" tests. Clearly, normalizing made a difference. The act of casting, and it's variables, do affect the resulting BHN of a bullet.

Test Results:
"As Cast" Condition
  Wheel Weights Wheel Weights Wheel Weights
  As Cast Annealed Heat Treated
  BHN 72 hrs BHN 72 hrs BHN 10 days
Average

14.74

29.90

27.20

S.D. 0.48 0.00 0.00
       
"Normalized" condition
  Wheel Weights Wheel Weights Wheel Weights
  As Cast Annealed Heat Treated
  BHN 72 hrs BHN 72 hrs BHN 10 days
Average 11.80 33.00 27.20
S.D. 0.00 0.00 0.00

     There is one variable still out there. Notice that in all results, the BHN of the wheel weight alloy dropped after 10 days. I have no explanation for this anomaly. The test was done again, and the same result was seen. I am open to suggestions.

     I now had a way to ensure that all bullets would be the same BHN before loading. But does it matter? How much of an effect does the BHN of a bullet have on accuracy? And more importantly, how does heat treating bullets effect accuracy verses using an alloy that already has the required BHN?

     I noted that when reading about heat treated bullets the author always makes the statement "Never size your heat treated bullets as that will remove the effects of heat treating" (sic). This always has laid in the back of my mind as an unanswered question. We are heat treating our bullets to raise the BHN, yet sizing the bullet removes the effects. What a minute, don't we also talk about shooting cast bullets a few thousandths over bore size? Are we not sizing the bullet as soon as it enters the throat? If we are (we are), would that not remove the effects of heat treating?

     I have just spent three months finding a way to ensure that all my bullets would be as close to the same BHN as possible, why go to the trouble if the act of entering the barrels throat removes the effects? Clearly heat treating works to reduce leading and allow higher velocities. That has been proven many times over. I know this myself as I have heat treated buckets full of 357 semi wad cutters with great success.

The Third Test:

     Another test was called for. I needed to know if the barrel throat and the act of resizing the bullet removed the effects of heat treating. Another 100 bullets were cast, normalized, tested, and then heat treated. After two weeks the bullets were tested again and the results recorded. In order to test the BHN of the bullet at the point it contacts the barrel (or the sizing die) I needed to test on the base band. Unfortunately this does not give a proper test result. Since the base band is not flat the resulting test dimple is egg shaped. I decided to go ahead and record the size of the dimple across it's shortest side. I would still be able to see any change in the BHN, I simply would not be able to relate the measurement to an actual BHN value.

     I now needed a way to send the bullet down range with as little damage as possible. I used a light load of Unique and fired the bullets into a stack of old lawn cushions three feet thick. This proved entirely adequate. After firing 100 rounds at 25 yards, 61 rounds were recovered. Of those 61 rounds, 34 were found to be in perfect condition not having run into another bullet or left the Dacron stuffed cushions.

     Those 34 bullets were then washed in mineral spirits and tested again on the base band. The results were interesting. As I suspected, the trip through the throat and down the barrel does remove some of the effects of heat treating.

     *Note that the first column is the results of normal BHN testing before the bullets were processed.

     *Note that the column rows are not related. Sample 1 - column 1, is not the same bullet as sample 1 - column 2. There was no certain way to identify individual bullets for this test.

Testing bullet hardness after firing:

      Heat After       Heat After
Firing# BHN Annealed Treated Firing Firing# BHN Annealed Treated Firing
1 10.4 0.068 0.044 0.048 17 9.80 0.066 0.048 0.060
2 10.4 0.068 0.044 0.052 18 10.4 0.068 0.046 0.058
3 10.4 0.068 0.046 0.050 19 9.80 0.066 0.044 0.060
4 9.80 0.066 0.044 0.060 20 9.80 0.066 0.044 0.060
5 10.4 0.068 0.044 0.056 21 9.80 0.066 0.044 0.064
6 9.80 0.066 0.046 0.064 22 9.80 0.066 0.050 0.056
7 9.80 0.066 0.044 0.062 23 9.80 0.066 0.044 0.056
8 9.80 0.066 0.044 0.064 24 9.80 0.066 0.048 0.056
9 9.80 0.066 0.046 0.058 25 9.80 0.066 0.048 0.062
10 10.4 0.068 0.044 0.062 26 9.80 0.066 0.052 0.060
11 10.4 0.068 0.046 0.064 27 11.0 0.072 0.050 0.064
12 10.4 0.068 0.048 0.064 28 9.80 0.066 0.050 0.058
13 9.80 0.066 0.046 0.058 29 9.80 0.066 0.048 0.048
14 9.80 0.066 0.044 0.054 30 10.4 0.068 0.048 0.052
15 10.4 0.068 0.046 0.060 31 10.4 0.068 0.046 0.060
16 10.4 0.068 0.046 0.062 32 9.80 0.066 0.046 0.056
     

 

Average 10.0 0.067 0.046 0.059
For All 32 tests
        S.D. 0.33 0.001 0.002 0.005
For All 32 tests

     So why does heat treating work? I think we first have to understand what heat treating really is. It is not a replacement for a harder alloy, heat treated bullets are a different animal.

     When we quench a bullet in water we are not changing the BHN of the bullet. In fact the core of the bullet remains nearly the same. You can see for yourself by heat treating a bullet and then filing .030 off the nose and doing a BHN test. When we heat treat a bullet we are in effect case hardening, only the surface of the bullet is affected. The resulting BHN measured on the surface of the bullet is only a measurable result of the heat treating, the true BHN of the bullet as a whole is not changed.

     The next question that comes to mind is "do I need to expend the effort to control my resulting BHN when heat treating"? I have never seen a loss in accuracy from simply dropping cast bullets in water, and my previous testing showed that quenching resulted in the widest SD of any other method of heat treating. It is possible that the simple act of heat treating is all that is required? The resulting BHN not being that important so long as the bullet has been altered by heat treatment? I think it is possible that the BHN is simply a result of the heat treating and the case hardening is doing the real work of deterring leading. More testing is in order.

Conclusion

     I do not believe that testing cast bullets can provide a meaningful answer on which to base alloy mixing decisions, or to determine the alloy used. To really know the BHN of your alloy, I believe an ingot should be cast and normalized, to provide an accurate BHN measurement. Then bullets cast from that ingot and normalized. Only then can you be certain that your BHN is consistent across all bullets in the batch.

     However, testing cast bullets for BHN can be useful. I believe BHN testing a random number of bullets from a batch can provide meaningful insight on your casting technique. If you can cast 100 bullets in a session, and 10 bullets all test within a low SD, I think it proves your casting technique is consistent and you can be confident in your bullets. However, if your bullets test with a large SD, maybe you have become lax in your casting and it might be time to pay a bit more attention to your process.

     I also think that normalizing bullets after casting has promise. In the game of accuracy, we are willing to buy custom molds, methodically prepare and prep cases, trickle powder charges, and sort and weigh each bullet. Why not give the same consideration to our bullet's hardness?

     It is also my belief that heat treating a bullet reduces leading because the base of the bullet is not affected by the trip down the barrel. The 'case hardened' bullet base acts much like a gas check, protecting the bullet from the pressure and heat of the burning charge. It certainly would not take much to increase the alloy's ability to withstand the heat and pressure. Many shooters have used wax wads, lube wads, even plastic wads to achieve the same result. How much consideration should go into managing the resultant BHN? The real question is, will it matter? I don't have an accurate enough rifle to determine if a large BHN SD will affect accuracy, but when I do, testing will resume.

Wheel Weights And Heat Treating Cast Bullets

Bill McGraw

     I use some 429421 bullets cast along with all my RN and SP rifle bullets to measure the BHN before and after heat treating. I have a few FN rifle CB's that I can more accurately measure BHN, but I rarely use them. My WW alloy was from an 1800# supply we melted down many years ago. Part of it had 1% Tin added. BHN of both WW and WW+1% Tin was 12 BHN within a week of casting bullets. BHN immediately after casting was about 11, and maximum BHN has been 13. I no longer use straight WW; I mix mine with 6 BHN roof sheeting or cable sheathing at 1:1 or 1:2 for softer alloy that casts much better, cuts sprues cleaner, and heat treats to 27-28 BHN from 450F; 465F will get a few more BHN numbers, but is not needed. I get 9 BHN with 1:1 and 8 BHN from 1:2 ratios. After annealing the noses, the nose BHN will be nearly as cast; the base BHN will be reduced by 3-4 BHN but does not reduce the effectiveness of hi-vel hunting loads.

     I use an old LBT BHN tool that has been calibrated and checked with another. I assume I am within a few points of a correct BHN, if not accurate. I have used a mix of WW:Foundry type of 1:12 giving about 13.5 BHN. Heat treated at 450F gave 31 BHN and after 7 years still gave 28 BHN. However, the noses after annealing gave 11, not 13.5 BHN. Regardless of that baffling result, I was more surprised at the 28 BHN reading after 7 years in my shop with temperatures from freezing in winter to high 90's in summer. Some of these were successfully test fired last week at 2150 MV in my 308 Win. using the RCBS 30-165 Silhouette CB. My Foundry type alloy has some copper content but I do not attempt to remove it; it can be mixed with WW at 4:1 ratio WW:FT and heat treated to well above 30 BHN. FT by itself casts poorly and tends to have large voids and a purple "color" tint. The WW/Pb alloys tended to reduce BHN to 23-24 from 27-28 BHN after a year. I have kept several dozen samples of alloys, some as cast and others heat treated and can measure them for long-term BHN changes. I have been able to heat treat to 35 BHN with a mix of WW/Linotype at 4:1 ratio, but 450F is about the maximum temperature possible before slumping of the alloy occurs. I tend to use 425F for this mixture. It makes very good looking bullets, and they age well without the oxidizing that straight WW has after a year or more of storage.

     There are many factors I can't verify and one is the exact alloy. I use bullet weight as a factor of each mould, "color" and texture of the casting, and BHN as tested to estimate the alloy. I don't attempt to measure the exact temperature each melts or starts to harden as temperature is reduced. I have not found linotype to harden with heat treatment; if it does, it must not be pure linotype and must have Arsenic in a trace amount. I am neither a metallurgist nor an engineer. I have read most of the usual publications for casting in re to alloys and heat treatment. I don't subscribe to a lot of nonsense I've read or seen on the various lists and there is plenty of nonsense about alloys. Bill Ferguson and Dennis Marshall are two I respect; C.E. Harris and Bill Davis are two others I believe report accurate articles on alloys.

     I have a small amount of chemically "pure" lead I have used to measure the volume of my moulds; the same is done with used linotype. I have some Tin, but rarely use it; it does not improve casting with my WW/Pb mixtures. I have a large supply of linotype "rules" that is still in the paper wrappers; I have not used any of that supply but assume it to be rather pure linotype or a super mix to "improve" used linotype. My current kitchen oven is accurate to +/-5F. I check the temperature with grocery store oven temperature gauges. Some kitchen ovens can cycle up and down by 25F or more. It is best to test a few sample CB's to the maximum temperature for slumping and then reduce the temperature by 10-15F just to be safe from melting or slumping any CB's. I have annealed CB's in the kitchen oven just for testing the effects of oven temperatures of 450-250F with timing periods of 5 minutes to 30 minutes. One effect I noticed of alloys is that heat treating at 450F and oven cooling to room temperature reduced the as cast BHN by 1 or 2 BHN points; this tells me that CB's cooling on a pad after casting do not cool consistently, that oven cooling without quenching will give a more consistent BHN reading. Merrill Martin reported on this effect.

 

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