Leading - hard or soft alloy better...?

[AJMD429]

Seems like there is disagreement out there...

Let's talk bullet lead alloy. Most bullet companies use the common bullet mixture of 2% Sn(tin) 6% Sb (antimony) and 92% Pb (lead). The Bullet Works chose to use a different mixture of 2%Sn (tin) 8%Sb(antimony) and 90%Pb (lead) in order to get a special mixture. The Bullet Works has contracted with a lead smelter to make this mixture for the company. In order to get this mixture it has to be purchased in either 10 or 20 thousand pound lots. The big lots allow the bullet alloy to be controlled very closely for the highest quality possible. In all bullet alloys the more tin and antimony in the lead , the better the bullets! Antimony is powdered and does not melt at normal lead melting temperatures, so it needs a medium to allow it to mix or homogenize with the lead. The tin and lead mix very well and the tin allows the antimony to stay homogenized in the molten lead mixture in the bullet mold. The only problem is, Antimony runs over $8 a pound and Tin is $8 a pound as well. Alloying these two expensive metals with lead quickly raises the cost of the bullets therefore most companies choose to use the cheaper alloy. The 2% 8% 90% alloy that the Bullet Works has chosen does cost more and takes more time to cast, but yields a much harder, tougher bullet. This is easier on the barrel and eliminates barrel leading normally associated with lead bullets. The hard tough bullet alloy is better for taking steel targets down because the lead bullet is tough and stays together longer. The Bullet Works is using Magma Bullet Lube which is put in at 120 degrees temperature and with 60 psi air pressure to assure the lube is in the groove when the bullet is loaded. You will find that all bullets sold by The Bullet Works are resized by pushing them through the resizer by the base instead of the nose. This is to keep the base concentric with the sides for the most accurate bullet possible. All Pistol bullets sold by The Bullet Works are bevel base which allows them to be loaded with less chance of shaving the sides of the bullet which robs accuracy. It is the endeavor of The Bullets Works to deliver the very best bullets to the shooter at a very competitive price. If you will notice we only sell in larger quantities trying to keep the price competitive .

Most cast bullet shooters don't know a lot about the properties of the lead alloy they're shooting because they haven't been educated about it. If you want to learn a little bit about some important cast bullet facts, then please read on.

A common conception is that when it comes to lead bullets, harder lead equals less leading. This is a false perception! To explain this surprising statement, it is necessary to discuss the physics of getting the bullet out of the barrel and how lead residue comes to be deposted in the bore. When the powder charge ignites, pressure is generated. This pressure is measured in “copper units of pressure” (CUPS) and expressed in thousand of pounds per square inch. The heavier the powder charge, the greater the CUPS. Naturally, the purpose of generating pressure in the cartridge case is to force the bullet out of the case mouth and on down the barrel.

Lead is a soft metal. Its hardness is expressed on a standard scale, called the Brinell Hardness Number (BHN.) The BHN of the bullet interacts with the pressure generated by the burning powder. The mechanism of this involves the effect of the generation of thousands of pounds per square inch of pressure which causes the base of the bullet to expand, or “obturate”. Properly obturated, the base will have expanded beyond its original diameter which has the effect of “sealing the bore” against the explosive pressure of the gases burning behind it. Properly sealed, and working in conjunction with the lubricant in the lube groove, the bullet will thus not allow gases to escape forward from around the base of the bullets, which prevents it from shaving lead from the bullet body and forcing it into the bore grooves (otherwise known as “leading”.)

This failure to obturate (“seal the bore against onrushing gases”) causes leading which is a chore to clean and is a major obstacle to accuracy.

I tend to believe this comment:

Many gun owners refer to hard cast bullets as 'lead' bullets. In most cases, they do not understand the drastic differences or they would not use such an inaccurate generalization. This generalization is as inaccurate a generalization as referring to all motorized vehicles as Volkswagens.

Hard cast bullets may contain some lead and be grey in color, but that is where the similarities stop. Hard cast bullets can be formulated of numerous alloy mixes (antimony, silver, tin, etc) containing some lead, but the alloys make the bullet much harder than pure lead. Pure lead has a Brinell hardness # of about 4. Most hard cast bullets will have a Brinell hardness # of 11 to 30 and as such are several times harder than lead.

Generally speaking, a properly designed, sized and lubed hard cast bullet will not leave lead alloy deposits in a rifled barrel, but pure lead bullets will almost always foul a barrel to the point of a total loss of accuracy (with very few rounds fired) and perhaps to the point that the barrel will split or worse. ( see my essay on 'Dangerous Pure Lead Cowboy Ammunition' ) I am employing many abstractions here, as there are a number of ways to make a hard cast bullet foul your barrel and make a pure lead bullet not foul, but on the whole, what I have written in this paragraph is accurate.

Missouri Bullets goes on to explain their rationale:

Lead is a soft metal. Its hardness is expressed on a standard scale, called the Brinell Hardness Number (BHN.) The BHN of the bullet interacts with the pressure generated by the burning powder. The mechanism of this involves the effect of the generation of thousands of pounds per square inch of pressure which causes the base of the bullet to expand, or “obturate”. Properly obturated, the base will have expanded beyond its original diameter which has the effect of “sealing the bore” against the explosive pressure of the gases burning behind it. Properly sealed, and working in conjunction with the lubricant in the lube groove, the bullet will thus not allow gases to escape forward from around the base of the bullets, which prevents it from shaving lead from the bullet body and forcing it into the bore grooves (otherwise known as “leading”.)

This failure to obturate (“seal the bore against onrushing gases”) causes leading which is a chore to clean and is a major obstacle to accuracy.

An optimally hard lead bullet is simply one which obturates at a given pressure sufficiently to seal the bore against the gases which would otherwise “cut through” the soft lead (called “gas-cutting”, forcing molten lead into your rifling. A bullet which is too hard won't obturate and seal the bore, because the gas pressure is insufficient to expand the base of the bullet. A bullet which is too soft at a given pressure will experience excessive base expansion and vaporization of the lead, causing leading.

There is a formula for optimal bullet hardness which is simple and it is worth knowing:

Optimum BHN = CUPS / (1422 x .90)

The CUPS of your reloads is published in the reloading manuals. Take a typical .45 ACP load, using a 200-grain LSWC bullet – 5.0 grains of Bullseye. This load develops 900 FPS and is in common use among IPSC and IDPA gunners. The reloading manual shows that the pressure generated by this load is 20,000 CUPS. So, the formula for optimal bullet hardness is

20,000 / 1279.8 = 15.62

There it is! For this application – shooting a 200-grain LSWC at 900 FPS requires that you use a bullet with a BHN of 16 to 18 (round upwards a couple of BHN points for flexibility.)

You may be asking why shooters don't know much about this whole bullet hardness optimization business. The reason is basically that the large manufacturers, for ease of production, use a standard alloy for all of their cast bullet construction, an alloy which has a Brinell Hardness Number of approximately 24. Why do they do this? It's simple – one standard alloy simplifies logistics for the big manufacturers and, equally importantly, a bullet this hard ships well by standing up to getting dinged around during transportation. The fact that their bullets are too hard and cause leading and aren't very accurate because of improper obturation is something they'd really rather you weren't aware of. This explains why neither their packaging nor product information will ever refer to the BHN of their products.

Along those lines, how many boxes of cast bullets – from any source – state the BHN on them?

At the Missouri Bullet Company, we optimize bullets for your intended application. We don't take a “one size fits all” approach to manufacturing your bullets. We work with certified analysis foundry alloy in two hardnesses in order to provide you with the bullet hardness that works best for you. One is 2% tin, 6% antimony, balance lead for harder bullets at 18 BHN and the other is 1.3% tin, 4% antimony, balance lead. While it is expensive for us to maintain a dual supply of alloy, the payoff is in the fact that we can offer you a choice of bullet hardness.

[earlmck]

The Missouri bullets explanation jibes with my perceptions of how it works. The others fellows are maybe oversimplifying the situation.

About 50 years ago I bought the first revolver I had ever owned -- a Colt Python 357. Along with a belt and holster the shop threw in a box of Remington 357 ammo -- full power 357 load pushing a swaged pure lead bullet. This gave me the most magnificent barrel leading it has ever been my pleasure to see. Some years later I discovered that the same bullet loaded to 38 Special velocities is a very pleasant and clean shooter. Subsequent adventures with barrel leading have been nowhere nearly as severe as that first pure lead 357 experience and have mostly been of the "too-hard at too-low pressure" type.

My one exception to the "mostly been of the "too-hard at too-low pressure" type" was a box of .358/150 grainers I bought from a place which had always produced a decent bullet. The business had just been sold and included both a bullet casting business and a shotgun shot business. The new box of bullets could not be shot at any velocity I tried without bad leading. The bullets felt hard to the "fingernail" test but would not shoot. I guessed that the new owner had cast handgun bullets from the metal used for the chilled shot -- high antimony and almost no tin -- and that such an alloy is impossible to work with. I melted those bullets in with my regular bullet mix, cast into my regular 180 grain LBT bullet and everything shot fine thereafter.

On another note, somewhere back in my college days I was poking around in the University library and came across an article on alloying bullet metals. I copied a graph from that that resides in my loading notes notebook yet today (unfortunately I didn't think to include the source notation for the graph). According to that graph, the standard 2% tin/6% Antimony/92% Lead mixture gives a hardness of 16, while adding 2% more Antimony as done by Bullet Works only raises the hardness to maybe 17: certainly no vast increase in hardness.

[Chuck 100 yd]

Bottom line is,once the bullet is matched to the chamber throat ,normaly .001"-.002 over groove diameter, the alloy is matched to the chamber pressure. Low pressure = softer bullet , high pressure = harder bullets. Most lubes available today will work but experimentation to find the best one for you will be needed.

[AJMD429]

Maybe this...?

http://castboolits.gunloads.com/showthr ... alculators

[Sixgun]

Doc,
Like Earl and Chuck 100, I too have been casting for over 40 years and one thing I have found out.....there are no steadfast set of rules on what works and what don't work.

Before I cast for a newly acquired gun, I already have in my mind what velocity I want for the intended purpose I want. I take some measurements and go from there, pulling the info from my head on what needs to be done.

To be a master caster and make all kinds of different types and vintages of guns to run...and run right, it does take a lifetime of experience that cannot be learned from a stack of books.....or scientific conclusions.-----6

[Griff]

Cast bullet shooting is ever so much more than hardness (alloy) & pressure (velocity). Bullet dia. to groove dia. fit, twist, lube, groove depth, bullet jump, even to powder selection; can all affect leading. No matter how you say it, how many words you use, to say hardness affects leading, is an over-simplification. And while both bullet makers touch on it, they don't delve into those details... oh wait... that might not sell "their" bullets!

[Chuck 100 yd]

For a new cast bullet shooter it needs to be kept simple. Overload of information on possibilities can cause them to give up before they even have a chance for success. Some people like to overcomplicate this subject. True,there are many variables possible but that all can come later. Just slug that bore,find a mold that casts a bullet slightly larger using clip on wheel weight lead. Pan lube them and get to shootin. Load data is plentyfull. Learn as you go after you get the basics down.

[piller]

This all is helping me. I have some 350 grain cast bullets in .458 that I have tried in my Guide Gun with less than spectacular results. The bullets do not have a gas check and do have a bevel at the base. Accuracy is mediocre with some odd muzzle blast patterns. I think I need to experiment with different powders and velocities. I have just used 30-31 with them so far. I wonder if a faster powder might work better.

[Grizz]

my experience is very limited because I buy my cast bullets. but I test them against each other to find what I look for in a hunting-slash-bear-STOPPER bullet.

based on this I value a hardcast bullet that is not frangible. I test this by shooting into tough firewood and examining the bullet path and bullet condition, AND by doing a hammer test, which involves setting the bullets on an anvil or concrete and whacking them with a two pound hammer. I don't hammer them flat, I hammer in a controlled and methodic manner to determine the alloy's resistance to deformation, something I value very highly. When I find this quality I know I have a bullet that won't deform passing through bear bones, giving me a kill shot from any angle.

my tests show up alloy strengths and weaknesses without having to rely on a maker's sales pitch. there are many bullets I don't use because they can crumble under testing.

coincidentally, the bullets I use have never shown any tendency to lead barrels to the extent that leading is ignored in all of my lead-only firearms.

I did not see gas checks mentioned as a deterant to leading. I am guessing that I don't need them because I trade throw-weight for velocity and rely on momentum for the results I prefer, rather than velocity and bullet deformation. But currently all of my cast bullets have them.

better to test and verify. you can ask bullet makers for samples and test them, and run that data against your casting alloy for the information value.

[Catshooter]

Yep. The only hard 'n fast rule in shooting cast is there ain't one.

In my experience, bullet fit is king, hardness a distant second. Of course I don't shoot pure lead, this is from wheel weight and harder.

A lot of guys shoot wheel weights in their Glocks, for example. In every single one of mine (more than 15 over the years) my bullets have to be water dropped (to increase their hardness) or they lead badly. Even when they're way oversized. This is with factory barrels.

On the other end of the spectrum, I run a cast from my .38-55 to almost 1,800 fps. The bullet is right about bore size or maybe a touch under. It should lead like mad! But I can shoot an entire silhouette season (about 500 rounds) and there's not a spec of lead in that 26 inch barrel.

Nope, no hard 'n fast here.


Cat

[Sixgun]

Yep. The only hard 'n fast rule in shooting cast is there ain't one.

In my experience, bullet fit is king, hardness a distant second. Of course I don't shoot pure lead, this is from wheel weight and harder.

A lot of guys shoot wheel weights in their Glocks, for example. In every single one of mine (more than 15 over the years) my bullets have to be water dropped (to increase their hardness) or they lead badly. Even when they're way oversized. This is with factory barrels.

On the other end of the spectrum, I run a cast from my .38-55 to almost 1,800 fps. The bullet is right about bore size or maybe a touch under. It should lead like mad! But I can shoot an entire silhouette season (about 500 rounds) and there's not a spec of lead in that 26 inch barrel.

Nope, no hard 'n fast here. . Cat

I hear ya Cat......back in the day when fooling with a gun and trying to make it work...reading books....talking to other people....testing load after load after load......then 6 months later I get that baby shooting 100%........then I think I'm the best there is and know it all, you know....could write a book on cast bullets.........then.....I get another gun and find out I don't know nothin'!!! -----6

[Griff]

For a new cast bullet shooter it needs to be kept simple. Overload of information on possibilities can cause them to give up before they even have a chance for success. Some people like to overcomplicate this subject. True,there are many variables possible but that all can come later. Just slug that bore,find a mold that casts a bullet slightly larger using clip on wheel weight lead. Pan lube them and get to shootin. Load data is plentyfull. Learn as you go after you get the basics down.

Yep, once you get fit, then you can go on from there. Other than two store-boughts, I cast everything else I use... a quite button... no... either WW hardened with linotype, pure lead or straight WWs.

[w30wcf]

There are other factors that come into play......namely bullet sectional density and burning rate of the powder. Bullet lube type is also another factor. Gas checked bullets add another dimension.

Combine too hard a bullet with a too fast powder and throat leading will be the likely result. Switch to a slower burning powder with a too hard bullet and all might be well.

Lower sectional density bullets (g.c.) can be made from softer alloys and be pushed to higher velocities without leading and good performance.

For example, in the .22 Hornet, a 45 gr. 12 b.h.n. g.c. bullet (low .13 s.d.) can be pushed to 2,650 f.p.s. with good accuracy and no leading. That won't happen with a bullet having a .20+ s.d.

In the same .22 hornet, a softer 20/1 lead/tin bullet (g.c.) (low .14 s.d.) will work just fine at 2,200 f.p.s. and give excellent expansion.


w30wcf

[Catshooter]

That's the gospel Sixgun. I've fallen from the height of 'knowing it all!' more than a few times.

The first few rounds out of my 38-55 I couldn't believe there wasn't any leading. Everything I knew (up to that point) told me it was gonna. I'd opened up the mould just as far as I could and just gambled.

And then when I read about using a hot plate for mould pre-heat? How stupid could I get? Never thought of that and I've been struggling with iron moulds since '71. Sheesh.

Live and learn, that's all I can say.


Cat

[w30wcf]

Catshooter,
As we know, while we travel down the road of life, we always learn new things.

As far as preheating molds, Personally, I prefer the toaster oven since it heats a bit more evenly.
Right after I turn the pot on, I place the mold(s) into the Oven minus the handle retaining screws.

The oven is set at 450f since that is the temp I use to heat treat bullets for certain applications and find that it seems to be the ideal temp for preheating molds since the first cast produces good bullets.

Once the alloy is up to temp, I remove the molds with the handles and install the screws. Then begins the casting journey........

w30wcf

[Sixgun]

Jack Sr,
That's an interesting thought...a toaster oven! Here's what I do. In addition to setting them on the top of the furnace while the lead is still heating up, and right before the actual session begins, I go over the mould evenly with a propane torch......not directly, but waving it and making sure the condensation is burnt off and paying attention to the sprue plate also...probably 15 or 20 seconds with the torch. The actual heating of the mould comes from casting as fast as I can without smearing lead......This usually only takes about 5-7 fills and then those babies come out ready for the 5 gallon bucket of water.----6

[Catshooter]

You're right of course, at least one hopes that as one progresses down life's lane one learns a thing or two. I've got ex's though who argue with me having learned a thing . . .

A proper pre-heat sure does make a difference. Especially with Lyman's all steel moulds. Most of the time nowadways the first bullets to drop are keepers.


Cat

[KirkD]

As a general rule (noting exceptions as others have above), I use soft cast for velocities less than 1,500 fps. The only hard cast bullets (i.e., water-dropped) I use are for my 30-30 at 2,200 fps. Soft cast are especially useful when the groove diameter is so large that if one sized the bullets for it, one could not chamber the round. I've had a couple old antique Winchesters and Marlins that had a groove diameter at least .003 larger than my largest bullet I could chamber. With a soft cast bullet and a medium speed powder (Blue Dot, 2400, or IMR SR5749) with a pressure spike sharp enough to bump up the bullet, I could get five shot groups of between 1 & 3/4" and 3" at 100 yards in these cases.

On the other hand, I have had several cases where I tried commercial, hard cast bullets and got severe leading at traditional BP velocities, primarily due to the bullet not sealing the throat/bore.

[M. M. Wright]

To compliment the "you never know" theory, get a copy of Venterino's book on shooting the buffalo guns. You don't have to listen to Duke, just read the chapter where he has asked 5 or 6 World Champion silhouette shooters to write about their loads. The broad spectrum of their casting practices is amazing. Remember these are the best of the best. I really wanted to "pick their brains" but they do not agree with each other enough to establish a recipe for world class cast bullets. (boolits?)
There was a time when I did some commercial casting and I had a smelter that would hold 1000# plus. I used wheel weights and added pure lead and linotype until I could cast a 500 grain .458 bullet that weighed exactly 500 grains. That gave me a no.2 Lyman alloy. I still have about 20 of those bars cast in a linotype mold (22#) so enough to last the rest of my life but I still make 30# or so batches of 30:1 or 20:1 for my "special" needs. I like 30:1 for hunting bullets and make these batches with pure lead and tin.
I think bullet lube has a great deal to do with leading so all mine are lubed with SPG or something similar. There may some superior lubes for smokeless but I'm ignorant of them.