Leaded barrel?

[prickett]

Hi all,
I just cast my first ever set of bullets. I took them out and found leading in my barrel. I've been shooting lead forever (using other peoples bullets) without problem. Here are the specifics:

My current loads which don't lead my barrel (using other peoples lead bullets)
125 gr LRN 9mm sized .356
3.9 gr Titegroup
around 1000 fps
unsure of lube, but looks like its both Alox and some pan lube

The loads I cast that do lead my barrel
125 gr LRN 9mm cast with Lee 6 cavity tumble lube moulds (checked their size and they run about .360!)
3.9 gr Titegroup
around 1000 fps
tried twice tumbled in Lee Alox for one set and Alox/JPW/MS mixture for the other. Neither performed any better than the other (one lube was fired thru one gun, the other lube thru a second gun - both leaded)
Used lead bought from E-bay that was reclaimed shooting range lead
Water quenched it

From my understanding of leading, hardness of the bullet isn't that important, its the diameter of the bullet. Well, since my bullets are oversized, my understanding is that they shouldn't be leading. Being brand new to casting I'm out of ideas for solving the leading problem. What should my next steps be?

TIA

[lwknight]

Well, you need at least some hardness.
If the Evil-bay lead was melted from jacketed bullets, its probably almost pure lead.
you need to use a micrometer to verify that your boolits actually are what they are supposed to be also.

[thx997303]

Water quenching pure lead wont do anything, they may be too soft for your purposes.

Though they could be too hard if you have antimony in your alloy. Water quenched alloys are generally too hard for the 9mm.

[Three-Fifty-Seven]

Have you slugged your barrel, yes I know the 356 worked, but . . . what is the actual size?

Surprized 360 is fitting in the case without shaving . . .

What guns?

I'll admit I'm very new to this too! I have had a lot of leading in two of my guns, just getting to either no leading, or just a tiny smudge . . . it has been frustrating, but when you find the right combo of alloy, size, powder . . . that will bring a :bigsmyl2: to your face!

[smilie=s:

[Shiloh]

Your pure lead id dropping at .360! What is the actual weight of the slugs??

SHiloh

[Three44s]

Though I have a fair amount of experience with revolver bullet casting, this past summer I embarked upon my first escapade with an autoloader. A 9mm Kel-tec.

My mold was the Lee TC tumble lub six banger and I used Titegroup at that "4" range too.

I got some leading but this is a NEW gun .......... but my usual break in proceedure was implemented:

USP (non-embedding abrassive bore paste) and then CorrosionX to coat the bore.

But the striking difference between you broke in gun and my new one is that my alloy was known to me.

Genuine wheel weight alloy plus a fair amount of tin to assist in good fill out of those little microgrooves in the Lee tumble lube mold.

WW's have some starch to them and tin helps some as well.

Your factory lead boolits likely were quite a bit harder than some unknown range reclaimed lead.

I would also refrain from Titegroup until you get a handle on your leading ....... it's snappy enough that it isn't helping much. Go with UNIQUE.

Yes, your factories slugs worked with TG but just take my word for it ...... when you are up to your arms with aligators ....... why feed them at the same time .......... TG is snappy.

Three 44s

[prickett]

Some additional info:

Just mic'ed a larger sample of bullets and found them anywhere from .355 to .360. The .355's ones might be what is causing the problem.

I'm going to hand select bullets in the .356 - .357 range and see if they give leading.

This begs the question:

Do others of you having Lee 6 cavity moulds see this same type of discrepancy? The 6 cavity mould seems kind of useless if each cavity drops a different sized bullet.

I'd be ok if the cavities all dropped .356 or larger, because I could size them (can you size TL bullets?). But what can I do with an undersized cavity?

[243winxb]

But what can I do with an undersized cavity? Make all you bullets larger in diameter and size them. First add antimony and 2% tin to you alloy,Air Cool. Antimony will make the bullets larger. For the mould you can try this from Lee >
Increasing mold diameter

If you need the mold diameter of your cast bullets to be increased just slightly, there is a way to accomplish this with negligible ballistic results.

With the mold open, be sure you liberally lube the mold blocks in front of and behind the bullet cavity. Place a small section of cigarette paper or writing paper to the lubed block . This prevents it from burning.

When casting the bullet, the diameter of the bullet will be increased by the paper width. You can actually go up to about .010 before you begin to see lead flashing appear. While the bullet will be slightly "out of round", this very minimum amount will not effect accuracy or the manner in which the bullet travels through the forcing cone and barrel of your gun. http://www.leeprecision.com/cgi/faq/index.cgi < Lee Tech Assistant

[lwknight]

The casting discrepencies are usually a product of the molds heating up and cooling and varying casting temperatures.

[Down South]

I just cast my first ever set of bullets. I took them out and found leading in my barrel. I've been shooting lead forever (using other peoples bullets) without problem. Here are the specifics:


Just mic'ed a larger sample of bullets and found them anywhere from .355 to .360. The .355's ones might be what is causing the problem.

The Lee mould shouldn't be dropping boolits with that much difference in diameter. Since you are new to casting your technique may need work. It is possible that debris like a small piece of lead on the face of one of the blocks may have been holding the mould halves open on some of your casts.
Lee moulds tend to cast small so some of your smaller readings may be correct. Once you have checked the mould over for anything that will not allow the blocks to close fully I would make a few casts with it and then check the boolit diameter from each cavity. To check the mould, hold it up to a bright light while closed and see if you can see any light through it. If you can see light between the mould halves then there is an obstruction holding them open.
Another problem may be the way you hold the mould closed. If this is a Lee six banger then do not hold the sprue handle while filling the mould.

Your alloy can be a problem. It would be nice if you could mix the range scrap you have 50/50 with clip on wheel weights. Most range scrap that I have fooled with tests out to be almost pure lead. You may be able to use it like it is for low velocity loads. For the load you are using my preference for starting out would be ACWW or 50/50 WW & range scrap.

[buck1]

Holding the handles tight with the same pressure may be part of the trouble. It happened to me when I was getting started and still pops up from time to time.
I have also found range lead to be on the soft side.
You may try filling the lube groves with a non tumble lube. Others have had great luck with tumbleing lubes but its never been too great for me. ....Buck

[fredj338]

The commercial cast are rpetty hard, range lead, unless it has a lot of antimony, won't gain much by water dropping. Just a suggestion, ditch the TG. It burns hotter than almost any other powder & cause a lot of leading grief w/ softer slugs, JMO.

[HeavyMetal]

Sounds like you have a few "bugs" to work out.

Here's some observations I have made from past experience with fellow shooters:

Range lead is usually 22 rimfire (pure) and the remains of jacketed rounds melted down, again pure lead. My thought is this alloy is way to soft for 9mm.

My experience with pure lead is it is very hard to get consistant boolit unless the pot is very hot, again pure lead likes 775 to 800 in my experience.

The Lee 6 bangers are a little more difficult to sort out, add to that the "newbie" factor and this to may account for some of your diameter difference.

Tumble lube boolits come out of the mold and are supposed to be "ready to shoot" most of the time they are pretty fat! In your case your getting some "skinny" (355) and "fat" (360)
The skinny ones don't fit and may allow gas cutting and the fat ones are, most likely, "shaving" as they are seated! This will remove any lube from them during the seating process! Leading is almost a "gimme" under these conditions!

My suggestions to help out:

Go find some clip on WW metal, make sure it is in it's "manufactured" form right off the wheels! Now you are certain to have some antimony in the alloy that will harden as you water drop.

I would not mix these with your soft lead until you cure your problem then, and only then, can you consider mixing the two metals. I would suggest 1 Lb soft to 9 Lb WW.

Fire up your lead pot and either put the mold on it to heat up during pre melt time or go find a hot plate to set the mold on while your waiting for the alloy to melt. Try to set the mold on the heat source in a way that the sprue plate come in contact with the heated surface this will help base fill out.

Grasp the mold handles firmly but not in a "death" grip! Do not hold the third handle which is only for opening the sprue plate!

If your ladle casting pour one cavity at a time until the mold is full. If your using the Lee ladle smack your head against the wall and go get a Lyman or RCBS ladle!

If your using a bottom pour pot stick your mold underneath it and start your pour with the cavity nearest the handle in the position to be filled first! Hold the mold so the far end is higher than your starting point!

Now start your pour and pull the mold towards your! What your trying to accmplish is t get the alloy to "climb" the sprue plate from the first cavity to the last and leave a fair amount of sprue puddle on top! This will take some practise I assure you!

Once you've made up a supply it's time to QC! First you want to check and see how many are filled out correctly, do not accept "almost" if it is not filled out it goes back in the pot!

Now check those remaining for diameter and sort into piles. Lube and load these as a "lot" and do not mix the boolits. This way you can determine which diameter the gun likes and adjust your casting technique in the future to suit the gun.

I will also suggest you make sure that the "fat" one are checked ( pull one after seating) to make sure they are not shaving when seated!

This should get you on the right track and may give you more questions to ask.

Please ask them!

[Willbird]

The first time you run a TL mold it can be hard to see if they are filling out properly. The quickest way to find the small ones is to run them thru the lee push thru sizer.

Bill

[Three-Fifty-Seven]

I would also refrain from Titegroup until you get a handle on your leading ....... it's snappy enough that it isn't helping much. Go with UNIQUE.

Yes, your factories slugs worked with TG but just take my word for it ...... when you are up to your arms with aligators ....... why feed them at the same time .......... TG is snappy.

Three 44s

I am still working out my load, and I too was recomended by a local gunshop to use tite group, so I bought a jug a few days ago, just about as much leading as Bullseye (a very fast powder!) If I knew at the time I bought it, that it was about as fast as Bullseye, I wouldn't of bought it.

I'm loading 38 Spl but just as a example . . . Bullseye will give me a 2" five shot group @10 yards (with lots of leading), Tite group 2.5" (Also lots of leading!), BlueDot 1 25/32" (small amount leading) Trail Boss 2 3/16" (Just a tiny smudge of leading!)

[243winxb]

Prickett, Here is a good read on Oven Treating with Water Dropping for 9mm after you fix you diameter problems. http://www.castpics.net/memberarticles/arsenic.htm

[fredj338]

I am still working out my load, and I too was recomended by a local gunshop to use tite group, so I bought a jug a few days ago, just about as much leading as Bullseye (a very fast powder!) If I knew at the time I bought it, that it was about as fast as Bullseye, I wouldn't of bought it.

You have learned a couple of new lessons. I have probaably never gotten accurate advice on ahything gun, ammo or relaoding related from a gunshop employee. Most just have a little LE or military expe. & that is far from the level needed to give any advice. The other is TG. BE is faster on the burn rate chart, but TG burns at a higher temp. One reason so many report issues w/ leading & TG. Do more research for yourself, study reloading manuals & burnrate charts then talk to experienced reloaders for some insight. WHat's experienced, well I can only tell you it is not reloading for one or two cartridges.:roll:

[chris in va]

I have the same problem, except leading with very bad accuracy problems. Everything has been water dropped WW so far, but I cooked up some towel dropped and played with the crimping function on the seating die, sans FCD this time.

The water dropped boolits were quite hard after sitting for a few days. I couldn't so much as dent them with my fingernail. Not even a mark.

[MtGun44]

Too hard is more likely to lead than too soft in pistols. Too soft will usually bump up to
fill the throat/bore. Too hard will work fine if large enough to fill the throat/bore. If
undersized (a very common situation) it will lead like heck and be very inaccurate. One
of the most common offenders is the 9mm Luger, esp with European guns which seem to
have mostly oversized bores. Apparently, US gun makers are experienced with .38/.357
Mag guns and make a real effort to make 9mm barrels smaller than .38/.357 barrels, so
the problems are a bit less common.


Bill

[Jayhem]

With LEE molds I found that I have to manually align the blocks with a leather gloved hand as I'm putting the mold halves back together since Lee molds tend to not want to match up nice when hot without some manual encouragement.

[thx997303]

You need to lube up those alignment pins there Jayhem.

If they're not lubed enough to the point you have to coax them closed, they're going to gall and exacerbate the problem.

[Jayhem]

You need to lube up those alignment pins there Jayhem.

If they're not lubed enough to the point you have to coax them closed, they're going to gall and exacerbate the problem.

I asked at my local gunshop if they had an appropriate lube to lube the molds with and no one knew what could be used. I have heard that Alox cannot. What should I lube my pins with?

[fourdollarbill]

Well, Lee mold instructions advise to use solid alox for lube and I have used it for a long time. Since I joined this forum a few days ago I found people claiming it is bad. It works for me.

[HORNET]

The problem with using beeswax or boolit lube is that it migrates to where you don't want it and degrades after a while to a hard brown gunk that blocks the vents and doesn't lube anymore. Other lubes that have been used successfully are high temp anti-seize, moly-disulphide spray, dry graphite spray, and synthetic 2-stroke oil. The most recommended one BY FAR has been Bullshop's Bullplate lube. See the Bullshop link at the bottom of the page.

[canebreaker]

HeavyMetal:
I didn't see where you sized your boolits.

Lubing molds:
I use 40w sae oil, lube hinge and alignning pins. Just a drop and wipe off. Repeat every 40 or 50 pours.

Alignning pin alignment:
tighten hinge bolt till rear of handles has less than 1/32" movement up and down when open.

Clean up:
I wash my molds with mineral spirites and a tooth brush, then soapy hot water, rinse and use a hair dryer so steel won't rust. Relube, wipe down and store.

Molds are smoked at the beginning of every pour.

[243winxb]

Lee method
Bullet mold lubing

Aluminum molds require occasional lubrication. A technique that works well is to have a glob of hard, stick-type bullet lube (like Lee #90007, but any alox/beeswax lube will work) about the size of a .45 slug rolled into a football; when the mold gets hot, touch one end to the aligning grooves along the sides of the mold block, on the underside of the sprue plate, and on the steel pins along the bottom of the mold block. Use sparingly, as if any gets into the mold cavity it will cause wrinkled bullets.

Lack of lubrication will cause the mold blocks to mis-align, or the sprue plate to gall the top surface of the mold.

Be sure to remember to "smoke" the mold which helps the mold release the freshly molded bullet without having to use "persuasion". http://www.leeprecision.com/cgi/faq/index.cgi I have never smoked or lubed a mould yet, but i dont use Lee.

[TAWILDCATT]

the poster has 6 cavity molds they have pins that align.you might try less powder to see if the bullets lead .that would help to tell if their to soft.I hav 8 6 cavity and have no trouble,also are you running the melt hot lee molds need to be hot.
how are you measuring are you using caliper or mikes.mikes are better as long as you dont crush the bullet.

[prickett]

the poster has 6 cavity molds they have pins that align.you might try less powder to see if the bullets lead .that would help to tell if their to soft.I hav 8 6 cavity and have no trouble,also are you running the melt hot lee molds need to be hot.
how are you measuring are you using caliper or mikes.mikes are better as long as you dont crush the bullet.

Thanks to everyone for advice and tips.

To debug, I think I'm going to do the following:

Deliberately cast my bullets large, then run thru a Lee Sizing die to get a consistent diameter. I can then worry about the inconsistent sizes at a later time.

Load using W-231 rather than TiteGroup. *amn! Just bought an 8 lb jug of TiteGroup!

Am also going to cast some .45's (I've only done 9mm's so far). See if the .45's lead or not at their lower velocity.

I bought 100 lbs of recycled range lead which now appears to be pretty soft. Is buying antimony and mixing it with that lead the best way to harden it? I read a little about antimony and there were safety warning about dealing with it. Also, not sure my Lee melter heats up enough to melt it. Anyone?

[HeavyMetal]

Canebreaker:
As Prickett does not have a sizer, as yet, and he was talking about using "selected" Boolits based on diameter I didn't want to suggest a specific diameter that might be mistaken for a "hard and Fast" rule. As we all know each gun will have it's own prefferences!

I now see he has chosen a course of action and I think it's a good one!

Prickett:
I have read here some guys have successfully blended antimony with "pure" lead. I think for a beginner this might be more work than you really want to tackle.

Heck I been casting boolits for 30 years and it's more than I want to tackle!

If you need to harden your alloy the two easist ways are find real clip on WW, Most will have a substantial Antimony content. Add a little tin as that helps the antimony and lead "bind" together. Tin content must be less than antimony content!

Or find some type metal such as Lino type. This may be harder to do than say!

In either case you'll need to know some basic alloy content:

Clip on WW are usually 95.5% lead, .5% Tin & 4% Antimony. Keep in mind stick on type WW are pure lead. Some Clip on WW have more Antimony ( and less lead) than I listed.

If you have a hardness tester you can make some good guess's about alloy content by the BHN number from your specific lot of alloy. The numbers I listed for WW metal will air cool and be 9 BHN. If the WW metal has more antimony in it they will go to 13 BHN or so and get much harder if you drop them into water from the mold!

Lino type is 84% Lead, 3% Tin and 11% Antimony this stuff will be 22 BHN air cooled.

Lead alloy's have been mixed and matched for years so not everything can be accepted at "face Value". Long ago I decided that if it was in ingot form the alloy was plain WW metal unless the seller could provide "real" documentation as to it's content.

I only accept an alloy as type metal if it is in it's original type format..

You can find more information on lead alloy's in several printed sources, Wolf Publishing had some cast boolit annuals and they are a great source for this type information!

At any rate these "Percentages" give you a basic idea of lead alloy make up. Adding "pure" lead to any of them will reduce the amount of tin and antimony and increase the amount of lead which means a softer alloy.

Save your range lead for a time when you stumble onto some type metals.

Go to the auction sites and bid on WW metal that you can see in the picture shows clip on type weights. This should remove any doubt as to what it is and use this metal exclusively to cast your next lot of boolits for your 9mm.

Size and lube as you see fit and try them out.

Your idea to remove as many variables as possible from the problem is a god one, going t straight clip on WW metal is a step in that direction!

[Marlin Hunter]

With LEE molds I found that I have to manually align the blocks with a leather gloved hand as I'm putting the mold halves back together since Lee molds tend to not want to match up nice when hot without some manual encouragement.



Turn the open mold upside down (it will be upside down from dropping the boolits), then close it, then close the sprue plate.

[243winxb]

Is buying antimony and mixing it with that lead the best way to harden it? Yes. Rotometal sells Super Hard Alloy (30%-Antimony,-70%-Lead) http://www.rotometals.com/product-p/30_antimony_70_lead.htm For 9mm add 2% tin if air cooling. 45acp tin is not as important. If your going to water drop, you only need a total of 2% antimony in the alloy.

[prickett]

Is it ok to remelt my already cast - and lubed with Alox - bullets? I think I saw somewhere that alox causes a mess if thrown in a melting pot.

[prickett]

Yes. Rotometal sells Super Hard Alloy (30%-Antimony,-70%-Lead) http://www.rotometals.com/product-p/30_antimony_70_lead.htm For 9mm add 2% tin if air cooling. 45acp tin is not as important. If your going to water drop, you only need a total of 2% antimony in the alloy.

Could you explain your comments on tin? Why do you need tin for 9mm but not .45? My understanding of tin is that it allows lead to flow easier into moulds. Does it have a second purpose? And, why is it only needed in 9mm if air cooling, not water cooling?

Also, is there a rule of thumb for required BHN hardness by caliber (and/or velocity)?

[HeavyMetal]

The rule of thumb for alloy hardness, and this is still up for major discussions, is by pressure not by caliber.

If you have, or if you know, someone that has the second edition Lee reloading manual look in chapter 10. This is a very nice explanation as to BHN and pressure and give you an idea of why some alloys lead and some don't.

Lee does not provide any load data that they tested themselves but they do provide a lot of data other manufactures have provided over the years. Pressure readings are included for many of the loads and many first time reloaders are amazed at the pressure levels the 9mm works at.

As for tin and antimony? For years reloaders believed Tin was a hardening agent in lead alloys. It is not! Tin is a serfactant and allows lead to flow better as you sermised. Antimony is the real hardening agent, along with a touch of arsenic ( the small percentage of this is already in most "pure" lead)

You need Tin for two reasons: it helps "flow" and it helps "bind" the antimony to the lead to form a working alloy that does not have "lumps" or "hard" spots in it when casting.

We have several metal suppliers on site and some have a good price on WW duplicate alloy as well as sweetener metal to add to pure lead.

Do some reasearch it's interesting whats out there.

[Three-Fifty-Seven]

Is it ok to remelt my already cast - and lubed with Alox - bullets? I think I saw somewhere that alox causes a mess if thrown in a melting pot.

I would dump them in my ingot pot, but not the pot you cast from, just me . . . it burns off like flux . . . stinks too!

[243winxb]

Could you explain your comments on tin? Why do you need tin for 9mm but not .45? My understanding of tin is that it allows lead to flow easier into moulds. Does it have a second purpose? And, why is it only needed in 9mm if air cooling, not water cooling?

Also, is there a rule of thumb for required BHN hardness by caliber (and/or velocity)?
Water drop harding alloy needs 2% antimony. Grain-boundary strengthening or Hall-Petch strengthening makes the bullet harder. The more antimony the faster the bullet will reach it full hardness level. Smelting produces many different metals, check the metal weight. % in my link above. Swaged or cast, dont matter, heat treating/water drop still works if antimony is in the alloy. Its a proven fact oven treating gives more balanced harding from bullet to bullet, then just droping from the mould. Large amounts of tin is not needed or wanted in water dropping. For air cooled 2% tin is needed for velocity over 900fps. Why > Lyman>
Quote:
While antimony is used to harden the bullet, the mixture of tin is critical, for while antimony mixes with lead in its molten state, it will not remain mixed when it solidifies. If tin were not added, we would have pure antimony crystals surrounded by pure lead. A bullet of this type , while it feels hard , would certainly lead the bore and eliminate all potential for accuracy.. In a lead-tin-antimony mixture, the antimony crystals will be present just the same, but they will be imbedded in a lead-tin mixutre. As the bullet cools the tin will form around the antimony-lead keeping your bullets from leading the bore.

Obturate simply means to fill or plug. Cast bullets take the rifling by a process called swaging, same as a jackted bullet. This is why all cast bullets are sized groove diameter or .001" or more larger. Lyman #2 alloy will work with any cast bullet. No water dropping needed.

-



Lead is normally considered to be unresponsive to heat treatment. Yet, some means of strengthening lead and lead alloys may be required for certain applications. Lead alloys for battery components, for example, can benefit from improved creep resistance in order to retain dimensional tolerances for the full service life. Battery grids also require improved hardness to withstand industrial handling.

The absolute melting point of lead is 327.4°C (621.3°F). Therefore, in applications in which lead is used, recovery and recrystallization processes and creep properties have great significance. Attempts to strengthen the metal by reducing the grain size or by cold working (strain hardening) have proved unsuccessful. Lead-tin alloys, for example, may recrystailize immediately and completely at room temperature. Lead-silver alloys respond in the same manner within two weeks.

Transformations that are induced in steel by heat treatment do not occur in lead alloys, and strengthening by ordering phenomena, such as in the formation of lattice superstructures, has no practical significance.

Despite these obstacles, however, attempts to strengthen lead have had some success.


Solid-Solution Hardening

In solid-solution hardening of lead alloys, the rate of increase in hardness generally improves as the difference between the atomic radius of the solute and the atomic radius of lead increases.
Specifically, in one study of possible binary lead alloys it was found that the following elements, in the order listed, provided successively greater amounts of solid-solution hardening: thallium, bismuth, tin, cadmium, antimony, lithium, arsenic, calcium, zinc, copper, and barium.

Unfortunately, these elements have successively decreasing solid-solution solubilities, and therefore the most potent solutes have the most limited solid-solution hardening effects. Within the midrange of this series, however, are elements that, when alloyed with lead, produce useful strengthening.

A useful level of strengthening normally requires solute additions in excess of the room-temperature solubility limit. In most lead alloys, homogenization and rapid cooling result in a breakdown of the supersaturated solution during storage. Although this breakdown produces coarse structures in certain alloys (lead-tin alloys, for example), it produces fine structures in others (such as lead-antimony alloys). In alloys of the lead-tin system, the initial hardening produced by alloying is quickly followed by softening as the coarse structure is formed.

At suitable solute concentrations in lead-antimony alloys, the structure may remain single phase with hardening by Guinier-Preston (GP) zones formed during aging. At higher concentrations, and in certain other systems, aging may produce precipitation hardening as discrete second-phase particles are formed.

Alloys that exhibit precipitation hardening typically are less susceptible to over aging and therefore are more stable with time than alloys hardened by GP zones. Lead-calcium and lead-strontium alloys have been observed to age harden through discontinuous precipitation of a second phase Pb-Ca and Pb-Sr in lead-strontium alloys as grain boundaries move through the structure.


Solution Treating and Aging

Adding sufficient quantities of antimony to produce hypoeutectic lead-antimony alloys can attain useful strengthening of lead. Small amounts of arsenic have particularly strong effects on the age-hardening response of such alloys, and solution treating and rapid quenching prior to aging enhance these effects.
Hardness Stability. For most of the two-year period, the solution-treated specimens were harder than the quench-east specimens. Other investigations have also shown that alloys cooled slowly after casting are always softer than quenched alloys. The alloys with 2 and 4% Sb harden comparatively slowly, and the alloy containing 6% Sb appears to undergo optimum hardening.

Application. Because of the detrimental effect of antimony on charge retention, the effort to reduce antimony contents of the positive plates in lead-acid storage batteries has led to the trend of replacing eutectic alloys with a Pb-6Sb-0.15As alloy. Battery grids made of this arsenical alloy will age harden slowly after casting and air-cooling. However, storing grids for several days constitutes unproductive use of floor space and results in undesirable interruptions in manufacturing sequences.

Although large-scale solution treatment of battery grids might be difficult to justify economically or to achieve without some distortion, quenching of grids cast from arsenical lead-antimony alloys offers an attractive alternative method of effecting improvements in strength. The suitability of quenched grids can be assessed by comparing with the hardness level that battery grids require in order to withstand industrial handling (about 18 HV, the hardness of the eutectic alloy). The alloy containing 2% Sb clearly does not respond sufficiently to be considered as a possible alternative. The 4% Sb alloy, however, attains a hardness of 18 HV after 30 min, and the alloys that contain 6, 8, and 10% Sb could be handled almost immediately.


Dispersion Hardening

Another mechanism for strengthening of lead alloys involves elements that have low solubilities in solid lead, such as copper and nickel. Alloys that contain these elements can be processed so that no homogenization results; most of the strengthening that occurs is developed through dispersion hardening, with some solid-solution hardening taking place as a secondary effect.
The resulting structure is more stable than those developed by other hardening processes. Dispersion strengthening also has been achieved through powder metallurgy methods in which lead oxide, alumina, or similar materials are dispersed in pure lead.








---



Gas Cutting To Soft Alloy -Picture what happens! Softer lead is in a putty form when slammed with tons of pressure. When it enters the rifling it is "flowing" and can expand to obturate(to close or obstruct) in the rifling which is good to a point. Eventually, you exceed it's ability to seal and it "skids" farther down the bore where the lead stops "flowing" and is harder again. Now the rifling marks will not fill themselves and you have gas leakage.
Pressure has a larger effect then heat, the boolit will never get hot enough to melt but hot gas will cut the sides from it's pressure.

The problem is when slammed with tons of pressure, you no longer have the bullet shape you started with.

obturation-Once the bullet is engraved, if the land/groove width varies, then the seal is broken on the trailing edge. How many times have you seen barrel leading "follow the rifling"? That is a sure sign that the bullet was too hard for the pressures generated by the load. This is why bullets of moderate hardness are desirable, by obturating they can seal this trailing edge. At extremely low pressures (e.g. 600-700 fps) obturation isn't quite as important since at these low pressures blow-by isn't as much of a problem and the lube serves as a floating fluid gasket and seals the gases (thereby limiting blow-by). Unfortunately, at the higher pressures that most sixgunners operate at, the lube gets blown out the muzzle if it doesn't have obturation playing a supporting role.

So, for routine sixgunning applications what do we want from our cast bullet alloy? In the 800-1000 fps range we should probably keep the alloy at a BHN of 12 or below. From 1000-1400 fps, 12 to 16 is a very useful range of hardness. For velocities of 1400 to 1700 fps, this window slides up to 14 to 20. Above 1700, linotype at a BHN of 22 is an excellent choice.






Casting bullets

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Bullet Sizes & Weights – How to Vary Them

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if you bullets drop from the mould undersize using 50/50 -WW& Pure Lead, you will need to add more wheel weight to increase there diameter. Lead shrinks more as it cools in the mould then wheel weights. Linotype can be added to increase bullet diameter also.
Quote:
The bullet diameters and weights presented in this list
are based on the use of Taracorp’s Lawrence Magnum
bullet alloy (2% tin, 6% antimony, 1/4% arsenic,
91.75% lead).
Bullet diameters and weights will vary considerably
depending on the lead casting alloy used. This variation
can be as much as 1/2% on the diameter, and 8% on
the weight among the most commonly used casting
alloys. For example, a .358-158 grain bullet might
show a diameter variation of .002", and a 13 grain difference
in weight.
Of the most commonly used alloys, wheel weights (.5%
tin, 4% antimony, 95% lead) will produce bullets having
the smallest diameter and heaviest weight, with
such bullets running approximately .3% smaller in
diameter and 3% heavier than bullets cast with
Taracorp's metal. Linotype will produce bullets with the
largest diameter and lightest weights. This alloy will
produce bullets approximately 1/10% larger and 3%
lighter than Taracorp. Other alloys of tin and antimony,
with antimony content above 5%, will produce bullets
with diameters and weights falling between those cast
from wheel weights and linotype.
Alloys containing little or no antimony will cast considerably
smaller than wheel weights and in some cases
will produce bullets too small for adequate sizing.
Within the limitations given above, the weight and
diameter of a cast bullet can be adjusted by varying the
alloy’s antimony content.
The size and weight of bullets of a given alloy will also
vary according to casting temperature. Higher temperatures
will result in greater shrinkage as the bullet
cools, thereby producing a slightly smaller and lighter
bullet than one cast of the same alloy at a lower temperature Cast Bullets

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Heat Treating/Water dropping of bullets was invented to reduce the amount of costly alloy using tin and antimony. United States Patent 5464487 http://www.freepatentsonline.com/5464487.htmlI fine water dropping to be a waste of time when casting bullets with the proper alloy. Water and hot alloy can explode it they come in contact with each other. While antimony is used to harden the bullet, the mixture of tin is critical, for while antimony mixes with lead in its molten state, it will not remain mixed when it solidifies. If tin were not added, we would have pure antimony crystals surrounded by pure lead. A bullet of this type , while it feels hard , would certainly lead the bore and eliminate all potential for accuracy.. In a lead-tin-antimony mixture, the antimony crystals will be present just the same, but they will be imbedded in a lead-tin mixutre. As the bullet cools the tin will form around the antimony-lead keeping your bullets from leading the bore. I have read that this process can take up to 24 hours as the alloy oxidizes. If your going to size a cast bullet, wait 1 day. Plain base bullets to 1400fps, gas checked to 2200fps without leading. Check Lee lead testing chat for the maximum pressure allowed for you alloy hardness. Also us the formula > Bullet's BHN x 1422 = Pounds per square inch. http://en.wikipedia.org/wiki/Obturate Cast alloy bullets should never Obturate. The bullet is sized over groove diameter by .0005" to .001" Some rifles will like as much as .003" over groove diameter. Casting bullets is really simple most times. If the bullet diameter is correct as it drops for the mould, you are good to go.. Pure lead will be undersize in diameter, unless using a Black powder/muzzle loader mould. High antimony will be on the large size. Always make sure you have 2 % tin in the alloy and you will never have leading. 22LR bullet have little to no tin and only 3 % antimony at the most. The some how dont lead the bore. This is where a very good lube is needed. Lee mould are regulated using 10-1 lead/tin alloy and should drop from the mould .003" larger than the diameter listed on the mould.. Lyman uses there #2 alloy to get the correct bullet diameter as it drops for the mould.90% lead , 5 tin, 5 antimony. To make #2 alloy, use 5 1/2 lbs wheel weight, 1lb 50/50 lead/ tin bar solder, 3 1/2 lbs pure lead. FLUXING-Heat the alloy for about 20 minutes until it becomes liquid. A gray scum will rise to the surface, this is Tin. Tin being lighter , will float to the top of the mix. Fluxing will recombine the tin -lead-antimony mix. To flux , drop in tallow, beeswax or bullet lubricant (beeswax),. Stir the mixture, scrape the sides/botton of the pot. Black and brown impurities will rise to the surface for skimming. Zinc wheel weight should be avoided as zinc keeps the bullet from filling out completely, sometimes using more heat will help. Avoid any/all Bismuth alloys. Alloys containing high percentages (52% +) of Bismuth will grow bigger in diameter after 3 days. Radiation Shielding has Bismuth in it. PDF file here> http://www.aimspecialty.com/AIM-flie...g%20Alloys.pdf More on Bismuth here > http://www.alchemycastings.com/lead-...ts/fusible.htm A high content of Bismuth will cause the mix to melt at a much lower temperature. Lyman - Heat Treatment of Cast Bullets to Harden Them

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Quote:
Q: Is there anything I can do to make the bullets harder?
A: Cast bullets can be heat treated to increase their hardness providing your alloy has some antimony present. To heat treat your bullets: Cast your bullets in the normal manner, saving several scrap bullets. Size your bullets but do not lubricate them. Place several scrap bullets on a pan in your oven at 450 degrees and increase the temperature until the bullets start to melt or slump. Be sure to use an accurate oven thermometer and a pan that will not be used again for food. Once the bullets start to melt or slump, back off the temperature about 5 to 10 degrees and slide in your first batch of good bullets. Leave these in the oven for a half hour. Remove the bullets from the oven and plunge them into cool water. Allow them to cool thoroughly. When you are ready to lubricate, install a sizing die .001" larger than the one used to initially size them. This will prevent the sides of the bullets from work-softening from contact with the sizing die. Next apply gas checks if required and lubricate. These are now ready for loading.

[243winxb]

Also, is there a rule of thumb for required BHN hardness by caliber (and/or velocity)? A 15 BHN will work with any pistol and rifle as long as there is 6% antimony & 2% Tin in the alloy. Lees chart showing what BHN is needed for the PSI of the load. http://i338.photobucket.com/albums/n420/joe1944usa/LeeChart.jpg

[243winxb]

Hear is a good chart to look at.http://i338.photobucket.com/albums/n420/joe1944usa/Alloy_20090610_1.jpg

[243winxb]

Everything you ever wanted to know about cast lead bullets in one book here. http://www.midwayusa.com/viewProduct/?productNumber=796528 Its how i learned 30+ years ago before the internet was born. Good Luck, Happy Casting. Happy New Year.

[prickett]

A 15 BHN will work with any pistol and rifle as long as there is 6% antimony & 2% Tin in the alloy. Lees chart showing what BHN is needed for the PSI of the load.

Wow! Thanks for all the info everyone.

Looking at the Lee Hardness Tester chart above and the Hogdon pressures, it'd suggest I need:

13 BHN for .45 ACP
23.8 BHN for 9mm
19.3 BHN for .357

That doesn't sound right. Or, did I misread the chart?

[243winxb]

Wow! Thanks for all the info everyone.

Looking at the Lee Hardness Tester chart above and the Hogdon pressures, it'd suggest I need:

13 BHN for .45 ACP
23.8 BHN for 9mm
19.3 BHN for .357

That doesn't sound right. Or, did I misread the chart? Not everone agrees with the chart. I have never tested hardness, except for my thumb nail. When i start casting , i check bullet diameter as soon as the 1st bullets are cool enough. They must be larger than my sizing dies. .452", .3575" .430" .310" If the bullets drops from the mould undersized , i add 1lb of linotype (10lb pot) to my indoor range scrap, till i get what i want. Shooting max loads in 44 PB to 1300 fps and 30 caliber to 2200 fps with GS has worked well so far. http://i338.photobucket.com/albums/n420/joe1944usa/th_CastBullets_20090207_004.jpg (http://i338.photobucket.com/albums/n420/joe1944usa/CastBullets_20090207_004.jpg)

[HeavyMetal]

Look like your read the charts right!

Nice of the guys to post both the Lee BHN chart and the Lyman alloy chart.

Keep in mind that you need to understand what pressure level the load you want to use generates and then cast from the alloy best suited for that pressure range.

As in all things there is no one size fits all application. You can alter your loads to use one alloy or you can have several different alloys for specific applications.

These days I have three alloys: one for high pressure stuff, 9mm, 44 mag, and rifle boolits BHN will be about 22

a second for mid range stuff: light 44's, 45 auto, 38 spec BHn is about 14

A third alloy is strictly target load stuff: about 5 BHN and made from a mix of stick on WW and a little tin. This alloy is strictly for my 38 wadcutter mid range loads specifically for my S&W model 52.

[prickett]

OK, this chart of BHN ( http://www.castingstuff.com/tester_hardness_cross_reference.htm ) makes more sense combined with the Lee Hardness chart than the previously posted hardness chart (on page 2 of this thread). The link in the previous sentence shows pure lead and wheel weights several digits harder than the other chart. With this chart, the numbers in the Lee chart are attainable.

Thanks again everyone for the outstanding information you are providing!

[243winxb]

Follow the link for complete data with Photos & Charts. http://www.fbi.gov/hq/lab/fsc/backissu/july2002/peters.htm [QUOTE] Forensic Science Communications July 2002 — Volume 4 — Number 3




The Basis for Compositional Bullet Lead Comparisons

Charles A. Peters
Forensic Physical Scientist
Materials Analysis Unit
Federal Bureau of Investigation
Washington, DC

Background.......Bullet Lead-Manufacturing Process.......Variation in Lead Composition Resulting from Manufacture.......Significance of Bullet Lead Data.......References


Background


When the physical markings of a fired bullet recovered from a crime scene are too mutilated for visual comparison or the firearm used in the crime is not recovered, the bullet can be compared with other bullets associated with a suspect by its elemental composition. When a crime-scene bullet contains the same analytical elemental concentrations (i.e., match in composition) as the bullets from known cartridges, a single source for these bullets cannot be excluded. During the manufacturing processes, thousands of lead specimens (bullets and bullet cores) are produced with analytically indistinguishable compositions. However, those lead specimens that share the same composition are generally packaged within the same box of cartridges, or in boxes of cartridges of the same caliber and type at the same manufacturing plant, on or about the same date. When the differences in element concentrations are small but analytically significant, a comparative examination can be used to differentiate among bullets made of different alloys or to exclude a single source for bullets of the same alloy.

Comparative bullet lead analysis was developed in the early 1960s by researchers at General Atomic (now General Activation Analysis, Incorporated, Encinitas, California) under a federal grant to develop uses for neutron activation analysis (NAA). Researchers developed procedures for analyzing such materials as gunshot primer residues, glass, paint, and bullet lead. The results of their research were published in U.S. Atomic Energy Commission Reports (Lukens et al. 1970; Lukens et al. 1970), the Journal of Radioanalytical Chemistry (Guinn 1982; Guinn et al. 1987), and the Journal of Forensic Sciences (Lukens and Guinn 1971). In one research effort, the group acquired and analyzed samples from bullet lead manufacturers. The results of these analyses confirmed that a cast billet poured from a pot of molten lead is relatively homogeneous, but that leads poured from separate molten batches are distinguishable. As a result, comparative bullet lead analysis has been adopted by laboratories and accepted by courts internationally (Andrasko et al. 1993; Blacklock and Sadler 1978; Brandone and Piancone 1984; Capannesi and Sedda 1992; Cohen et al. 1988; Desai and Parthasarathy 1983; Dufosse and Touron 1998; Gillespie and Krishnan 1969; Guy and Pate 1973; Kishi 1987; Krishnan 1973; Krishnan and Jervis 1984; Sankar Das et al. 1978; Sreenivas et al. 1978; Suzuki and Yo****eru 1996).

The NAA technique used at many laboratories has been replaced by inductively coupled plasma-optical emission spectroscopy (ICP-OES), previously known as inductively coupled plasma-atomic emission spectroscopy (ICP-AES) (Peters and Koons 1988). OES was adopted because people confused AES with auger electron spectrometry (Boss and Fredeen 1997). Since the 1970s, ICP-OES has been widely accepted and is the method of choice for most inorganic analyses (Koons 1993; Montaser and Golightly 1987). One advantage of ICP-OES is its ability to determine the concentrations of as many as 70 elements simultaneously in some samples. ICP-OES instrumentation is used in environmental, manufacturing, research, and forensic laboratories throughout the world and has been used by the FBI Laboratory in casework for the past 12 years. The ICP-OES procedure currently used in the FBI Laboratory can determine the concentrations of seven elements (antimony, arsenic, copper, bismuth, silver, tin, and cadmium) in most bullet leads. The main disadvantage of ICP-OES is that it is a destructive technique, requiring acid digestion of approximately 60 milligrams of each replicate sample of bullet lead.

Bullet Lead-Manufacturing Process

Lead used in the bullet-manufacturing process is generally obtained from secondary lead smelters where the raw material is made primarily of recycled automobile batteries. Under stringent environmental regulations, these smelters separate the batteries into plastic, acid, and lead components. This lead is then mixed with lead from other sources and melted in kettles with capacities of 75 to 100 tons. This scrap lead is reprocessed into ingots (also called pigs). Elements such as copper and tin may be present but are controlled within limits determined by the economics of the process and use of the product. For bullet manufacture, there are few physical requirements for the lead. Chiefly, the lead must be processable. Antimony may be added to harden the alloy, but its level will also vary with the requirements of the product and the economics of its use. Hardened lead is generally used in non-jacketed bullets, whereas soft lead (i.e., lead where antimony has not been added) is generally used in jacketed bullets. The other elements are present in trace amounts and can vary.

Lead is generally delivered to the bullet manufacturers in several forms: ingots which are 65 to 80 pounds (Figure 1); billets which are 100 to 300 pounds (often 125); and sows which are approximately 2,000 pounds (1 ton). If delivered in ingots or sows, the lead is remelted in 7- to 10-ton pots (Figure 2) along with lead waste from the manufacturing process that may include rejected bullets (coated or uncoated), excess lead from bullet shaping, or any other scrap lead in the factory. The molten lead is then poured into a billet mold (Figure 3) and allowed to cool and solidify (Figure 4). Wire is extruded from the billets and cut into slugs (Figure 5). The slugs are formed into bullets by swaging, then tumbled for smoothness (Figure 6), and loaded along with gunpowder into primed cartridge cases (Figure 7). The cartridges are then loaded into boxes, which are stamped with a packing code (also called lot number) (Figure 8).
Photograph of ingots of lead from secondary smelter.

Photograph of ingots of a pot containing source (melt) of lead at bullet manufacture.
Figure 1 Ingots of lead from secondary smelter Click to enlarge image. Figure 2 Pot containing source (melt) of lead at bullet manufacturer Click to enlarge image.
Photograph of lead being poured into billet mold.

Photograph of solidified billets of lead.
Figure 3 Lead being poured into billet molds Click to enlarge image. Figure 4 Solidified billets of lead Click to enlarge image.
Photograph of billets being extruded into wire and then cut into slugs.

Photograph of bullets are tumbled and polished.
Figure 5 Billets being extruded into wire and then cut into slugs Click to enlarge image. Figure 6 Bullets are tumbled and polished Click to enlarge image.
Photograph of bullets, cartridge cases, and powder assembled to make cartridges.

Photograph of cartridges packed into boxes stamped with coded assembly date.
Figure 7 Bullets, cartridge cases, and powder assembled to make cartridges Click to enlarge image. Figure 8 Cartridges packed into boxes stamped with coded assembly date Click to enlarge image.

Variation in Lead Composition Resulting from Manufacture

The composition of lead reflects its inevitable heterogeneity at the secondary smelter, where the source material is usually a variable mixture of virgin and scrap lead. Differences in each batch may be attributed to environmental contamination, variations in mold-erosion rates, and temperature variations. Typically, the extracted metal must be processed further before its final use. However, the ultimate goal is to produce an acceptable product at the lowest possible cost. One consequence of the economics is that variations in composition are tolerated as long as they do not adversely affect the physical properties of the products being manufactured. Maximum levels of certain deleterious impurities are defined and not exceeded; at the same time, alloying elements are kept between pre-established minimum and maximum levels.

When processing the lead to produce wire for bullets, the ammunition manufacturer may add rejected lead from previous runs, lead trimmings, rejected bullets (including copper-plated rounds), and virtually any other source of lead in the plant that may be recycled into the pot with the lead ingots. If it was not recycled, the scrap would become an environmental hazard. Thus, with the proportions of recycled materials undoubtedly varying from batch to batch, the composition of the lead mixture will inevitably vary.

This lead mixture occurring both at the smelter and the ammunition manufacturer provides meaningful information to forensic scientists. The homogeneity of each melt supplies an identity to a batch while it provides the ability to distinguish between batches. This enables bullets to be compared by the different mean concentrations of the elements in each. The variation of the concentrations within a source depends on both the homogeneity of the source and the analytical reproducibility of the instrument making the measurements. The number of distinguishable compositions that can occur in a given concentration range increases as the variability of the measurement is decreased. For example, if the antimony level in a melt of lead were known (with 95 percent confidence) to be 0.12 % +/- 0.1, it would not be possible to distinguish (with 95 percent confidence) an alloy that contained 0.20 percent antimony from this melt on the basis of the antimony level. On the other hand, if the variability was only +/-0.001, 28 distinguishable antimony levels could exist. With modern ICP-OES instrumentation, the high precision achieved (3-5 percent relative standard deviation) in determining most elements in lead results in millions of potentially distinguishable lead compositions. It is this ability to distinguish small differences, in fairly narrow composition ranges (e.g., 0.01-0.05 percent) of the seven elements determined, that results in a high degree of discrimination between different melts.

The overall composition of the lead product is fixed after the billet formation has cooled (Figure 4). At most manufacturers, other scrap is frequently added to the lead in the melting pot throughout the dynamic process of bullet lead formation. As a result, bullets made from continuous pours may be analytically indistinguishable over only one to two tons. In one study, five billets from each of two melts produced on consecutive days were sampled at Winchester Western Company in 1974 and were analyzed by NAA. The measured percentages of antimony, copper, and arsenic determined in these samples are presented in Table 1. These results show that, for each melt, the five billets made from that melt are indistinguishable in their concentrations of all three elements. The billets from different melts are readily distinguishable by the concentrations of antimony and copper, which are significantly higher in pour one than they are in pour two, and by the concentrations of arsenic, which are slightly lower in pour one than in pour two. In another study, a single billet was extruded into a wire that was subsequently divided into the top, middle, and bottom portions of a billet. These samples were collected and analyzed by ICP-OES, the results of which are presented in Table 2. The concentrations of each of the three elements exhibit no measurable variation among the samples, indicating that this billet is homogeneous from top to bottom with respect to the measured element concentrations.

The variability of the final product can be affected by the final step in cartridge manufacturing, the packaging of cartridges into boxes. As a result of casework, in which lead from many boxes of cartridges from major ammunition manufacturers was analyzed, it has been widely demonstrated that most boxes of ammunition contain bullets from more than one melt. As previously discussed, bullets produced from a single wire (i.e., from the same billet) are analytically indistinguishable. However, during the processes of cutting, swaging, finishing, and jacketing bullets; assembling cartridges; and packaging boxes; bullets from various melts are intermingled. This was demonstrated in a published study involving 200 bullets from each of four manufacturers (Peele et al. 1991). A small part of the results of this study is shown in Tables 3 through 6. For one box of cartridges from each manufacturer, the average concentrations of five elements in each of the distinctive compositional groups are shown. The results are typical of those found in the larger study. One conclusion from this study is that for the ammunition studied (.38 special caliber cartridges loaded with lead round-nose bullets) within each box of 50 cartridges, Federal has one or two compositional groups, Remington and CCI (Cascade Cartridge Incorporated) have approximately five compositional groups, and Winchester has as many as 15 compositional groups. Although each alloy is specified by the manufacturer to contain certain antimony content, its concentration varies from 0.58 to 0.81 percent in the box of Remington ammunition and from 0.24 to 0.66 percent in the box of Winchester ammunition shown in the tables. These levels of variability in antimony and the other trace elements account for a large number of distinct compositions of bullet lead.

Significance of Bullet Lead Data

Compositional bullet lead comparisons are possible because each melt of lead has its own characteristic composition. There are enough identifying elements with concentrations that are measurable with good precision in the lead alloy to distinguish among most melts. Years of analysis in the FBI Laboratory have demonstrated that the distinctiveness of a melt is defined not only by the number of elements measured but also by the relative scarcity of other alloys in that melt. Not all measured elements are equally effective at discriminating among lead sources, however. In general, for most lead products, the relative source discrimination power of the measured elements decreases in the following order: copper, arsenic, antimony, bismuth, and silver (Peele et al. 1991). Tin is not included in this list because in many lead sources it is not present at detectable levels. However, when tin is present, it provides excellent discrimination among melts of lead. Antimony, specified by the ammunition manufacturers, is alloyed with lead in order to harden the bullets. The other elements are present in trace amounts and can vary from one product to another. Bullet leads analyzed from CCI, Federal, Remington, and Winchester have contained up to 0.42 percent arsenic, 6.8 percent antimony, 2.5 percent tin, 0.2 percent bismuth, 0.22 percent copper, 0.031 percent silver, and 0.011 percent cadmium. The wide ranges in concentrations of all of these elements within sources provide for thousands of distinguishable melts of bullet lead at any one time.

The composition of a molten pot of battery lead can change because of volatilization of selected elements, segregation during solidification, as well as other factors (Schmitt et al. 1989). However, in experimental studies of bullet lead ingots, no compositional variations have been observed. That is, once a composition is created, it does not change appreciably merely by being held at the pouring temperature. Even if there are several compositions within a melt due to the factors cited, the probability of a random match between unrelated melts of material would still be low because of the huge number of compositions that could potentially occur.

The more practical reason for a compositional match is that the material more likely is derived from consecutively poured billets than from a random match among the millions of possibilities among unrelated melts of material. Accordingly, the assumption of homogeneity of the melt is a conservative approach because it results in an overestimate of the number of analytically indistinguishable bullets produced.

In order to assess the significance of a compositional match, it may be helpful to know the number of bullets that can be manufactured from a homogeneous melt. A simple calculation can determine the number of bullets that can be produced from one ton of lead, though the number per ton will vary according to the weight of the bullet. For example, a .38 caliber lead round-nose bullet typically weighs 10.23 grams, which is equivalent to 158 grains. There are 454 grams in a pound, and therefore 44 bullets of this caliber are produced per pound. Because as much as 20 percent of the lead can be lost as waste during production, only 35 bullets are actually manufactured per pound, or about 71,000 bullets per ton. A .22 caliber long rifle lead round-nose bullet weighs 2.6 grams, which is equivalent to 40 grains. Therefore, with allowance for waste, approximately 140 bullets per pound or 280,000 bullets per ton can be produced. To appreciate the significance, compare this with the fact that there are approximately 9 billion cartridges produced annually by ammunition manufacturers in the United States.

In addition to the number of bullets manufactured within one melt, other factors must be considered, such as the distinctiveness of the melt, the distribution of ammunition, the relative concentration of the elements, and the date of manufacture. A manufacturer's distribution of cartridges throughout the United States is generally on a case-by-case basis. Since a single melt can be represented across many boxes of ammunition, it is expected that one source of lead can be distributed to more than one geographical area. Exceptions to this distribution might be bullets produced for law enforcement and the U.S. military, who order large amounts of ammunition at one time. If a packing code (lot number) is found on a box of ammunition, then the assembly date may be obtained from the manufacturer. Another factor that must be considered is a case where multiple shots of various calibers, manufacturers, and compositions are fired at a crime scene. If multiple compositions present in the crime-scene lead are analytically indistinguishable from lead groups in partial boxes of ammunition, it is much more likely that the crime-scene bullets came from those boxes than it is when only one compositional group is present.

All the aforementioned factors are considered when interpreting the compositional analysis data to determine if there is an association between specimens. If such an association exists, an example of the conclusion reached by the FBI Laboratory may read as follows, "The bullet removed from the victim and 10 of the 15 analyzed cartridges from the suspect residence are analytically indistinguishable from one another. Therefore, they likely originated from the same manufacturer's source (melt) of lead." This conclusion does not associate a bullet to a box but rather to a melt of lead that has bullet specimens within that box and perhaps other boxes.