Modern Reloading by Richard Lee

[GSSP]

In this book, page 134, Brinell Hardness & Maximum Pressure Chart. Any one familiar with this and understand how to use it? Have you used it? Does it work?

I'm referring to the intent on finding the max pressure, thus accuracy, for a specific bullet's BHN, not in reference to Lee's Machinist Pocket Microscope.

Thank you,

Alan

[Burnt Fingers]

http://www.lasc.us/Fryxell_Book_Chap...Metallurgy.htm

Harder is not always better.

[BigAlofPa.]

This might help?
https://missouribullet.com/technical.php

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 (PSI). The heavier the powder charge, the greater the PSI. 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.

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 = PSI / (1422 x .90)

The PSI 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 PSI. 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.

[GSSP]

I'm thinking I didn't make myself clear.

If I take a bullet i've cast, check it's BHN and find it's a 10 (for example), I would go to page 134 and try to find loads which are close to or under 12895 psi? Hoping to find someone who has used, successful or not, this system.

Caviat....I fully understand harder is not always better.

Thank you,

Alan

[Wheelguns 1961]

Cut and dry formulas like this aren’t the best way to go about this. First, I have found from experience that bullet fit is more important than bhn when it comes to leading. I cast alot of hollow points. These are normally around 10bhn, and have driven them to max pressure in 9mm, 357mag, and 327 fed mag. I also powdercoat. This helps also.

[Bookworm]

I'm thinking I didn't make myself clear.

If I take a bullet i've cast, check it's BHN and find it's a 10 (for example), I would go to page 134 and try to find loads which are close to or under 12895 psi? Hoping to find someone who has used, successful or not, this system.

Caviat....I fully understand harder is not always better.

Thank you,

Alan

Actually, the formula states that it needs AT LEAST THAT MUCH pressure to obdurate.

It doesn't state that the lead will withstand only that much.

Think of the pressure number as a floor, not a ceiling.

[USSR]

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

Optimum BHN = PSI / (1422 x .90)

The PSI 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 PSI. 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.)

Have never bought into the commercial caster's optimal bullet hardness formula. Why? Through personal experience. For example: like the .45 ACP load listed above, my .38 Special +P FBI Load generates ~ 20,000 PSI. I cast my own 160gr hollowpoints using a alloy with about a BHN of 8 (97 Pb/2.5 Sn/.5 Sb). I get perfect expansion and no leading. To say I need a bullet with a BHN above 15 for this load is ludicrous, but it does help the commercial casters sell their overly hard bullets.

Don

[Jniedbalski]

I use my lee load book all the time but found out I can push lead bullets softer than lee recommended in his book.

[gumbo333]

GSSP if you look into the archives you will find that last year I asked a question about the Lee manual and the pressure/ fps chart. Member Larry Gibson gave a stellar answer. Too long for me to recite here. Well worth a few minutes looking up though. Mr Gibson knows his stuff. gumbo333

[Burnt Fingers]

This might help?
https://missouribullet.com/technical.php

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 (PSI). The heavier the powder charge, the greater the PSI. 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.

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 = PSI / (1422 x .90)

The PSI 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 PSI. 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.

CUP and PSI are two different systems. CUP is not expressed as PSI. It's expressed as CUP.

[Cosmic_Charlie]

If your boolit fit and lube are good you can use lead quite a bit softer than you might think. I have settled on a BHN of 12 for most of my loads. Seems to be working fine.

[Carl.1]

Hello, i was just reading this, older post i know. But in the calculations i thought calculating bullet hardness to obtain the pressure that upsets the bullet was obtained by multiplying 1422 by the BHN of the bullet. I am confused as to where the calculations above come from as they do not reflect this. Apologies if i am missing something but .90 comes from where? As no bullet has a bhn of .90?

[Larry Gibson]

In this book, page 134, Brinell Hardness & Maximum Pressure Chart. Any one familiar with this and understand how to use it? Have you used it? Does it work?

I'm referring to the intent on finding the max pressure, thus accuracy, for a specific bullet's BHN, not in reference to Lee's Machinist Pocket Microscope.

Thank you,

Alan

The Lee formula, while it sounds good, is a dog that does not hunt. That is, unless you are using pure lead cast bullets. It only works then.

The reason being is we most often use a ternary alloy, binary alloy and sometimes a quadra alloy. The formula uses the constant factor for pure lead. That does not work with binary, ternary or quadra alloys which would, if you knew the exact composition, have a different constant. It is well proven and documented that ternary alloyed bullets with BHNs of 22 +/- can be pushed to 50,000+ psi at 2900 - 3000+ fps maintaining excellent accuracy without bullet failure from too much pressure. According to the Lee formula those bullets should have failed when the psi was in the low 30,000 range.

BHN is a useful tool [I use the Lee tool mounted in and old microscope] but it is only half of the "hardness" of cast bullets. The other half is malleability of the alloy.

[Carl.1]

The Lee formula, while it sounds good, is a dog that does not hunt. That is, unless you are using pure lead cast bullets. It only works then.

The reason being is we most often use a ternary alloy, binary alloy and sometimes a quadra alloy. The formula uses the constant factor for pure lead. That does not work with binary, ternary or quadra alloys which would, if you knew the exact composition, have a different constant. It is well proven and documented that ternary alloyed bullets with BHNs of 22 +/- can be pushed to 50,000+ psi at 2900 - 3000+ fps maintaining excellent accuracy without bullet failure from too much pressure. According to the Lee formula those bullets should have failed when the psi was in the low 30,000 range.

BHN is a useful tool [I use the Lee tool mounted in and old microscope] but it is only half of the "hardness" of cast bullets. The other half is malleability of the alloy.

Lees book refers to the BHN of bullets and the relation of different strengths in chapter ten, it is not relating just to pure cast..what formula are you refering to?

[rintinglen]

Bookworm called it correctly. That formula tells you the minimum pressure that will obturate the bullet. Lee stands it on it's head and it is just plain wrong to try and use it to determine optimum BHN. It is not useful, it doesn't work, and though it remains in print, it serves more to befuddle than to enlighten.

22 grains of 2400, (which is now over book), for many years considered THE load for a 429-421 from a 44 Magnum will shoot just fine at ~38,000 psi. That's with Lyman number 2, or ~15 bhn, which the formula tells us "optimally" should run at 19,197 psi, and should fail at some higher pressure point. If it still works at double the "optimal" then that optimal is not accurate.

If observation and testing disproves a hypothesis, that hypothesis must be rejected, and it's back to the drawing board. If empirical results do not conform the predicted outcome, the prediction is wrong, so it's time to get a better crystal ball.

Too often, mathematicians overlook the fact that a number is not the thing. The fact that your calculations give you number doesn't mean that that number means what you think it does. It is correct only as a calculation, which may or may not accurately relate to the phenomena you are comparing it to. But regardless, that formula is nearly worthless in bullet casting.

[Larry Gibson]

Lees book refers to the BHN of bullets and the relation of different strengths in chapter ten, it is not relating just to pure cast..what formula are you refering to?

Look on page 132. There you will find how Lee determines the "compressive strength" of the bullet. In the first paragraph under "Testing Bullet Strength" Lee states; "If you know the BHN of your bullets, multiply the BHN by 1,422 to find the ultimate compressive strength in psi."

It is the 1,422 that is the constant.

The fact showing why that dog doesn't hunt is born out every day by untold cast bullet shooters. I shoot a #2 alloyed WQ'd bullet at 2900 fps with a measured pressure of 50,000 psi +/-. The BHN [measured with Lee's BHN tool] of those bullets [164 gr 30 XCBs] runs 18 - 20. According to Lee's table based on finding the "ultimate compression factor" those bullets should fail at 26 to 28,500 psi. They do not. I have recovered several of those bullets fired into wetpack at 300 yards and they show absolutely no "compression" failure.

Other exaples are the bajillion cast bullet pistol bullets fired in 357, 41 and 44 Magnum cartridges. Many of them have been cast of COWW with a BHN of 11 - 12 +/-. According to Lee's table, based on the incorrect calculation of "ultimate compressive strength" those bullets should fail at 17,000 psi +/-. Yet they perform superbly at 34-36,000 magnum level psi [classic Keith loads w/2400] w/o any "compression" or alloy failure of the bullets.

There are many, many other examples used by most everyone on this forum posted every day. Lee's formula, and thus the table of "Brinell Hardness & Maximum Pressure Chart" is the dog that doesn't hunt because it is based on a faulty formula with incorrect input, i.e. the constant. Unless you know the actual compressive strength of the exact alloy used, the exact rate of acceleration and the strength of the bullet design to resist compression under that known acceleration rate Lee's simplified formula just doesn't work.

[TurnipEaterDown]

CUP and PSI are two different systems. CUP is not expressed as PSI. It's expressed as CUP.

This is not precisely true.
While more recent manuals do try to differentiate between measurements made using copper crushers as a measurement method (and for shotgun this used to be lead crushers, i.e. expressed in LUP) and piezo crystal sensor systems (expressed as PSI in most modern manuals), the CUP measurement is still a system to express pressured measured in PSI.

The copper crusher system uses/used a small cylindrical copper specimen sample mounted between a piston exposed to the cartridge case wall and an anvil, and after firing a user measured the permanent offset in the crusher to correlate to a semi statically applied load in a test machine to derive a PSI measurement.

The samples in the test machines are the correlation samples that when tested under differing loads (measured directly in pounds) allow the measurement of the offset (shortening) of the cylinder, and measurements of the unexposed sample's diameter, to generate a curve that allows the final measurement of a test sample offset to be thus related to the pressure required to create the amount of offset seen.

There are a couple issues w/ such a measurement system, and one of the predominant issues is the disregard of strain rate affecting the offset in the test specimen as compared to the correlation / curve generating specimen.
You will also note that the piston is not bearing directly on the gases, and the piston has a mass (takes force to move it at the rates applied).

So, Yes, copper crushers do "read" in Pounds per Square Inch.
The Reading is Not equal to a Piezo transducer, and that has to do with the set up of the test system and properties of materials.