Member Jackfish posted this information in another forum. Interesting links and formula.

http://www.lasc.us/CastBulletNotes.htm
Approximate "Maximum" Chamber Pressure For Lead Alloys (PSI)Plumbers lead, stick on WW 13,000 - (Black Powder Only)Wheel weights / clip-on 25,000 - Non-Magnum handgunloads, Rifles to 1,800 fpsLyman # 2 (alloy varies in Lyman cast bullet books) 35,000 - Magnum handgun & rifles to 2,000 fpsQuench-cast WW (dropped from mould into cool water) 48,000 - Magnum handgun& rifles to 2,200 fpsOven heat treated WW 55,000 - Jacketed velocities in handgunsand rifles with quality bore & balanced load
Bullet BHN / "Minimum" Chamber Pressure For Lead Alloys (PSI)The formula (from the pages of HandLoader Magazine) to determine at what pressure an alloy of given BHN will obturate the base of the bullet and seal the bore. If the bullet is too hard to obturate, gas cutting usually occurs on the base band on the non-driving side of the rifling and barrel leading is likely. Simply multiply the alloy BHN by 1,422. Example: Alloy BHN of 12 multiplied by 1422 = 17,064. An alloy of 12 BHN should be used with a load that develops a "minimum" of 17,000 psi. Need more info on minimum / maximum alloy BHN? These Glen E. Fryxell articles explain alloy BHN in easy to understand language. http://www.lasc.us/CastBulletNotes.htm

The exception to minimum pressure given in Jackfish's example is firelapping loads. BHN 12 is often used for firelapping, but the pressure is much lower, since the firelapping load is intended to just barely spit these out of the tube. That is not hot enough to cause gas cutting, despite being below minimum pressure.

Nick,

Not to a prude but just FYI the above info comes from another website and I also take issue with the min/max pressure data listed.

The first line alone is enough to get attention as “plumbers lead / stick-on WW’s� (a/k/a almost pure Pb) is listed as “maximum pressure 13,000 psi.

A little more FYI, muzzle loaders can develop operating pressures well in excess of 20,000 psi pushing a conical as can BP cartridges. Testing done using exact duplications of BPCR factory loads offered in 1886 produced a 100 round average operating pressure of almost 21,000 psi using bare bullets cast from pure lead and nearly 25,000 psi using the same weight PP bullets that were also offered in factory loads.

According to the info presented, clip-on WW’s are listed as 25,000 psi and 1,800 fps maximum. Now, in the second half of the info on “minimum pressure�, the example shown is for 12 Bhn alloy (what clip-on WW’s average) indicating this alloy requires no less than 17,000 psi.

Follow me here … to run a load that produces 2,280 fps, we would need to use “quench cast WW alloy�, roughly 18 Bhn based on the resultant velocity thus according to the information provide above. Now, when we look at the operating pressure of the load, this velocity is obtained using an average operating pressure of 24,050 psi. Using the minimum chamber pressure calculations above, 1422 (constant) * 18 (Bhn) = 25,596 thus indicating that the pressure obtained by the load is insufficient to obtrude the bullet alloy.

If we flip the order around, the 24,050 psi operating pressure indicates using a bullet alloy of clip-on WW’s or Lyman #2 however, according to the information, neither is capable of handling the 2,280 fps velocity … which technically is into the “heat treated� area according to the info.

My whole point being, working the numbers will take up your time riding out the long, cold winter nights but in most instances they don’t mean squat when it comes to what works and what doesn’t. The above load I used as an example can be duplicated using cast bullets in the .22 Hornet and .222 Remington.

Another thing is the (attn: MIKE G) is the .35 Remington and other “cross-over� and old time cartridges that are capable of using bullets that will provide high velocities but operate at lower than expected pressures with normal loads. Even more modern cartridges are fully capable of producing wide variations that are disproportional to the expected operating velocity and pressure.

Proper sizing of the bullet and cartridge case along with using the right lube and removing mechanical issues from the gun does more to improve performance of cast bullet loads than does the particular alloy. I’ve run strait WW alloy (not quenched or heat treated) above 2,400 fps and 35,000 psi without any fouling or accuracy issues.

Take this stuff with a grain of salt.

When you say "quench cast WW alloy�, roughly 18 Bhn " it seems to me you're adding a variable that is not in the article. Quench cast WW alloy may be 18 Bhn but it could also be 16 or 17 Bhn or occasionally higher. All dependent on heat of the mould, lead, and water temperature used as quenching agent. What I see in the article also is a speed of 2200 fpe as maximum that would relate to maximum chamber pressure for quenched WW alloy and you exceed that figure with 2280 right from the start albeit only 80 fpe.

So what I see in the first paragraph is a guideline for those that don't actually know what the Bhn of the alloy is but how it was cast and composition of the alloy. For those that know what the actually Bhn is then the second paragraph applies for minimum pressure as related with maximum pressure. These are only guidelines, not absolutes.

If I recall correctly this article originated from a article on Leverguns.com as a continuation of thought on Ken Easterlings article of "Is Your Bullet Weak Enough". You are right though........... take what anyone says with a grain of salt.

MarkW,

Please don't apologize for pointing out exceptions! Our purpose on the board should be technical truth, not faith in any one source's ideas. I notice the formula in the linked article is different from the Handloader article's formula. 1440 rather than 1422. Way too many decimal places to be practical. 1440 (3 decimal place precision) came from 3 x 480 (two decimal place precision). I would guess, seeing batch to batch hardness number variance in the bullets I've cast, that two decimal places is as much as any such theory could practically support. I would just use 1400 as being close enough.

My faith in the formulae is also limited. If I can knock a day loose to play with it, I will see if I can't do an FEA of obturation? My gut instinct is that any such formula would be valid for only one caliber. That's because obturation probably only needs to be one or two thousandths, regardless of caliber. For a given alloy, obturation as a response to pressure will be proportional to the size of the bullet, and therefore getting a couple of thousandths of obturation from a .458 should require a lower minimum pressure than, say, a .32 does.

Let me open another can of worms for this discussion. If you start with a wide enough bullet (say, .002" oversize), and you have no tight spots in the barrel to narrow it, why is obturation necessary at all? I once tried slugging a barrel with alloy cast bullets, and found you could not feel tight spots because the stuff is springy. Indeed, unlike pure lead slugs, pushing that same slug through the bore repeatedly proved just as difficult each subsequent time as the first (not counting initial engraving). The springiness kept that bullet a thousandth or so over bore diameter. So, why would that radial springing not constitute an adequate seal for bore gases? I think it would, and that what is being presented as lack of adequate obturation may actually be another phenomenon? Alloys like Linotype are not only harder than common casting alloys for bullets, but have lower melting points. I have to wonder if the correlation to hardness and leading blamed on gas cutting wasn't actually base melting and deposition? It would be easy to test, as a water-hardened bullet of a lower alloy would then show less leading than a same-hardness bullet of a higher alloy. Be interesting to try, anyway.

Another possibility is bad experiences by people who do have barrel constrictions. Revolver frame constriction of the barrel at the throat is particularly common, and can be up to several thousandths. Enough to resize a bullet below spring-back diameter and require subsequent obturation to get a seal as it goes further down the bore. That could fool people's perceptions of either maximum hardness or minimum pressure requirements. Lots of variables.

Ahh Ha! Pull out paddle and stir pot .... LOL

Gohon & Nick,

I am hard pressed to use the term "guideline" as I feel "observations" is more applicable term given the simple fact that what looks good numbers wise many times doesn’t mean squat to what’s actually going to happen in the real world. A guideline would mean there is some actual fact involved that directly equates to a “given� for a majority of applications. Arguing the wording is quite petty but it helps make my point that while the info is useful to some extent, it does not have a majority of hard-fact agreement obtained from actual testing conditions. This is not to discount the effort and expense put into compiling the info by those who took the time to do such, if it was not for people taking the time to compile information, we would still be firing rocks from a sling. The problem is that information such as this is often presented in a “matter of fact� manner which opens it up to be ripped to shreds by examples that clearly don’t fit the pattern….the end result is that those people/persons who put the info out in the first place often find themselves on the defensive from the attacks rather than simply carrying on a discussion about the info. Yes, I take issue with the info as it written but I do so for the sake of discussion and not with the intent to attack the presenter, I just like doing some tongue-in-cheek pot stirring to get people interested in the discussion….and it worked!

The "roughly 18 Bhn" is based on using the industry standard WW alloy of 95.25% Pb; 4% Sb; 0.5% Sn; 0.25% As 750°F melt temp, 5 second mold hold time. Not a total given if you're working with salvaged WW's and casting by hand but it's about where they'll drop if you're running a standard manual casting rhythm to maintain consistency but you are correct in that 18 Bhn is not a "carved in stone" figure, just an average point since as you stated, the actual Bhn can vary for any number of reasons. Trying to work with anything other than “average� for the sake of discussion is too difficult unless it turns out being novel length.

Nick hit the nail on the head and we’ve about beat this topic not only into the grave but people in china are complaining about the mole hill that is quickly turning into a mountain because we’re still beating the same topic for years now.

In my experience, cast bullet issues are caused by: Bullets that are too hard, bullets that are too small, mechanical issues with the gun (tight spots in bore / throat / chamber), mechanical issues with the reloading equipment (sizing die too small, crimping too hard, sizing equipment, seating dies), lube sucks … yadda yadda yadda

I’ve said it before, I’ll say it again and will continue to say it – the ultra-hard alloys came about mainly because other issues that are actually creating the problem were not solved, the simple answer was to make harder bullets but in reality it is simply putting a band-aid on an amputated limb and hoping it’ll hold.

It’s the same thing I ran into when I tried to explain to a fellow that he was getting considerable Cu fouling simply because he insisted that a 0.451� bullet was for any “.45 caliber� and there was no reason why it shouldn’t work in his rifle…problem was, the rifle was an older make chambered in .45 colt with a 0.455� groove diameter. I don’t care how you twist it, when you have 0.004� of slop between the bullet and the grooves, it’s going to leak gas which will cut the bullet and foul the bore. As Nick said again, guys will load a 0.357� ultra-hard cast bullet into a .357 mag and wonder why the forcing cone and cylinder end of the bbl is loaded with lead…. They never consider the fact that the bullet is squeezed down by the undersize chambers and is too hard to obtrude back out once it gets past the obstruction.

Then we have the GC issue that’s another whole can of worms that is sometimes the cause of Pb fouling instead of the cure. Use of GC’s is way over rated and completely un-necessary in the majority of applications where they are so commonly “mandated� based solely on velocity and/or operating pressure of a given load.

My “grain of salt� comment is not directed so much at the information itself but rather in the delivery of the information and at the massive amount of dis-information and myths that continue to be repeated, some are going on hundreds of years and are coming from alleged “experts�.

Nick, FYI it's "Mark Kw", the "Kw" comes from the shortening of my last name so as it would fit in the itty bitty block provided on the VIDS/MAF forms used for Navy aircraft... and it really makes things much easier when I am leaving a phone message for someone rather than having to spell out the entire name.

markkw, if I came off sounding argumentative that was not my intent. I've been reloading for many years but just recently got into the cast bullet arena so I doubt I could even be considered a amateur just yet. Reading through forum opinions and comments plus anything else I can get my hands on has so far been my only real experience except for a little less than 1,000 lead bullets I've cast, reloaded, and fired in my attempt to learn. When I find a site like lasc.us that has a article such the topic at hand and it is more or less a hard copy in print on their site I have to assume there is a endorsement of part if not all of the article on this site. This article along with several other articles on lasc.us gave me what I consider a pretty solid base to stand on as I developed a learning curve in bullet casting. Then I read a post in a forum (this thread) that rightly or wrongly seemed to debunk the entire article which leads me to lean towards the article of the topic instead of just another persons opinion. maybe I just read what you wrote wrong but it just seemed you were going outside the paramiters of the article to make a point.

One thing I have noticed is the people with the most experience and knowledge on pretty much any subject are the very people that seem to make something sound more difficult than it really is or need be. Just recently I found a older thread on this site about bullet hardness, softness, and accuracy that had 50-60 posts, mostly from experienced caster that were also engineers and by the time I finished reading the thread I not only had a headache but I wondered what planet these guys lived on.

I'm not a slow learner by any stretch but I do need guidelines to get started. Otherwise how would we know where the starting gate was.

Gohon,

No, I didn't read your reply as being argumentive at all, just discussion and that's what these forums are all about.

I started casting & shooting cast projo's about 29 years ago. Much like everyone else, I listened to and read everything I could find - no internet at that time, just a few books, gun rags and the wonderful gunshop BS.

I was never quite happy being limited to this or that and started experimenting and what I found was that many things the "book" says won't work, do in fact work quite well in the real world. It was through process of elimination that I figured out where problems started and why - the only "constant" you can absolutely depend on is that every gun is different.

When it comes to cast bullets, there is just a multitude of things that can either make or break the gun/load combo and if one doesn't explore all the possibilities, they are limiting themselves to operating in whatever rut they have chosen to follow.

I chose to point out the pressures associated with black powder because it is all too often repeated that the pressures are very low when it is not the case at all. Way back when, Noble demonstrated that a black powder load in a muzzle loader can develope pressures in excess of 100,000 psi under the right conditions. I haven't even seen "brown powder" mentioned in anything printed within the last 80 years or so yet it was capable of producing pressures and velocities that would still be considered quite acceptable for full throttle smokeless loads of our modern day.

Unfortunately, the only way to point out the fact that while some numbers info is good, it is not the "carved in stone" fact - the only way to point this out is by using examples that just pokes the information full of holes. As I said above, my intent wasn't to discount the work of the info providers but rather to just stir the pot and make people think.

It's like the argument over round balls vs sabot conicals in a muzzle loader. Toby Bridges and friends have been beating the numbers drum saying that their sabots deliver X energy and Y velocity at Z range in an effort to discount the terminal effects of a round ball. While the majority of people swallow this BS hook, line & sinker, at no time is there any countering point provided that alluded to the fact that PRB's produce their terminal affect in a completely different manner than a conical bullet does. If one doesn't make the effort to poke their dis-information full of holes with the facts, the point can never be made that a PRB with un-impressive numbers is often far more terminal than is a conical with impressive looking numbers. Same goes for the 300gr jacketed bullets in the .45-70 vs the old 450gr soft cast FN. The jacketed bullet companies are going to do everything in their power to keep you from realizing that a bullet you can cast yourself will more often than not produce far superior results than will one of the jacketed bullets you are buying from them.

It's like the alox lubes, the manufacturing & mining industries stopped using alox based lubes over a century ago because there was far better stuff available yet companies of today still sell a pile of it to put on cast bullets. Then you have the "clean" lubes that are simply colored wax that usually isn't worth crap as a lube but since it doesn't stick to your fingers, that becomes the major selling point - add to that the fact the hard-lube producers now get to sell you a lube heater to go along with their lube.

The info above isn't part of a money making ploy but it is still flawed to some extent and that needs to be pointed out. It's not just shooting related either, in my book on home workshops & garages I point out the fact that a number of books on the subject matter contain the statement "a table saw requires 10 sq ft of working room. Sounds great but as I point out in my book, if you have 10 sq ft of saw room, just how in the heck do you plan on stuffing a 32 sq ft sheet of plywood into that area?

Markkw,

Sorry for dropping one of the "k". I suspect I was typing too fast and just didn't lift the middle finger clear of the key far enough the make a second entry. This "egonomic" keyboard I'm trying to get used to is still tripping me up a bit.


Gohon,

Don't let complexity get discouraging. People who are more advanced in a specific area have almost nowhere to turn among the popular publications to see discussions at their level. It can be overwhelming to someone just starting out, but after a couple of years of active participation, you'll be contributing the same sorts of stuff.

One of the biggest problems in the whole firearms industry is that almost nobody can afford to do statistically significant testing. To determine something like obturation hardness across all calibers, just to get 90% confidence that your numbers were correct, you would need at least 21 guns of each caliber tested to produce a data point, and you would have to run through all the cast bullet alloys and sizing option combinations for each one. Then you would need an accurate way to measure the leading build-up differences. Probably by electrolytic removal and weighing on a laboratory quality scale, which is a slow undertaking. Way, way, expensive and time consuming. But, absent that sort of effort, about the only thing people can do is report their experience with a few guns, then wait for exceptions to be reported and try to allow for them.

And here we are!

For a beginner, I'll stick my neck out and say I have observed you can mold about anything in wheel weights and get good results if your bore has been firelapped and you have a good lube. You can add a little more tin to that alloy to promote mold filling and make the mold temperature slightly more forgiving. Just don't let the % tin exceed the % antimony if you are going to water harden because they will age (lose hardness) more rapidly if you do.

As Mark said, gaschecks are not a cure-all because they can be reduced by passing through undersize revolver throats or barrel constrictions, too, which renders them ineffective. There is just no substitute for correct gun geometry and a cast bullet matched to it. Learning to slug bores and revolver throats is something you would benefit from early in your cast bullet career, both to select correct size bullets and find problems that need to be reamed (revolver chambers) or lapped out. I wish I had learned about firelapping in the 70's, when I first started casting.

Nick,

Once you get used to that ergo keyboard, you'll never go back to a strait one again, just give it about a week.

You summed things up quite well. I'll tell you how I start building a load for a new gun...

1- Inspect for and eliminate all the mechanical issues you can find with the gun.

2- Slug the bore and find out what you've got to work with.

3- Check the twist rate of the barrel (sometimes they don't match the info provided by the mfg.)

4- Select a starting load and based on the velocity it will produce with a given weight bullet, select a bullet of corresponding length for the twist and velocity to ensure it'll be stable.

5- Make sure the bullet drops from the mold at 0.001"-0.003" larger than the groove diameter with strait WW (melt temp held at 750°F - 775°F & mold maintained at temp while casting)

6- Check your castings for obvious flaws; also check for: weight; diameter & roundness consistency.

7- Select a good soft lube and either dip or pan lube.

8- Compare the cartridge neck I.D. to the bullet O.D.. If the neck I.D. is more than about 0.002" smaller than the bullet O.D., it's going to cause deformation of the bullet upon seating making everything you've done to this point useless.

8a- Make sure the seating die top punch exactly matches the bullet nose shape you're using.

9- If everything checks out load ten rounds and see what they do.

10- If you encounter a problem anywhere along the way, stop right there and correct it before continuing, otherwise you're just wasting time.

10a- Make changes one at a time and document the cause and result of the change somewhere that you won't loose them.

Your numbers 3 and 8 are often forgotten and just assumed to be correct. Excellent pointers. Excellent list.

Nick, If I told you how long I screwed around wondering what was going wrong with a .308win, you'd laugh your @$$ off at me. Well, I guess I can't tease, how about 5 weeks!

Checked and double checked everything I could think of till one day .... I finally thought about checking the case neck. I honed the sizing die out about 0.007" and made a bigger expander ball .... whaddya know, finally got a group instead of a pattern. So my process #8 doesn't get missed anymore.

I do have to insert 8a too, I forgot this one last night - Make sure the seating die top punch exactly matches the bullet nose shape you're using.

I wish I had learned about firelapping in the 70's, when I first started casting.


OK "I'll bite" exactly what do you mean? :confused:

Check out the last FAQ for the firelapping overview.
http://www.beartoothbullets.com/faq/index.htm

Bye
Jack

Thank you Jack!

Another factor i sectional density. I have found that the lower the sectional density, the lower the b.h.n. required for trouble free accurate shooting.

Two examples of this are:
46 gr. .22 cast bullet (SD .13) 12 b.h.n .22 KHornet - 2,650 f.p.s.

120 gr. .30 cast bullet (SD .18) 12 b.h.n. .30-30 - 2,300 f.p.s. By comparison, a 180 gr. (SD .27) 12 b.h.n. bullet maxes out at 1,800 f.p.s. in the same rifle.

Food for thought.......
John

John,

I did some thinking about it and I have an idea. Can you give me the barrel lengths with which you achieved those velocities?

Thanks

unclenick,
.22 KHornet - 20" barrel - 12 grs. / 680
.30-30 - 24" barrel (micro-groove) - 34 grs. / 748

One additional note: in the .22 KHornet, I also tried a 30/1 lead tin mix just to see how fast I could push it until accuracy started to deteriorate - 2,200 f.p.s.:D Surprisingly, there was no leading even with the soft 30/1 alloy. NRA lube (50/50) was used in the tests.

John

John,

What I think your observations indicate is the result of columnar pressure. The acceleration in the barrel is analogous to subjecting the column of lead that is the bullet to a strong gravitational field (gravity is also an accelerated frame of reference). If you were to set bullets down on a surface in a strong enough gravitational field, the sides would bulge under the weight of the column and the nearer you got to the bottom, the more they would bulge because the pressure would be greatest there. Obviously, a longer, heavier bullet would bulge more than a lighter, shorter one. Constrained to a bore, the bulging force is greatest near the base of the accelerating bullet and adds to friction within the barrel. Thus, you cannot accelerate a longer bullet of a given hardness as rapidly as you can a shorter one before that friction becomes great enough to initiate leading.

How much effect there is will vary with the lube, but I thought it seemed, at least with your lube, that perhaps we could multiply peak acceleration by sectional density and insert a constant into the denominator that would give us a minimum Brinnel hardness number. That did seem to work out within 10% or so. Not too shabby. The problem is that to know the peak pressure you need an internal ballistics program. I thought I might get close enough using average acceleration based on the barrel length and the bullet’s muzzle velocity, but that substitution opened the results up over 25% in your three samples, so it isn’t really good enough. I tried the trick of using the square root of barrel length to compromise the significance of the barrel length, since peak pressure for a given load is reached early in a bullet’s travel and doesn’t change with barrel length. On the other hand, velocity does change with barrel length and cannot be ignored when considering the resulting muzzle velocity. That approach, together with a constant of 16,000 seemed to get the results of your posted data within bout 10% of one another.

Where:

w = bullet weight in grains
d = bullet diameter in inches
mv = muzzle velocity in feet per second
bl = barrel length in inches

Then:

SD = w ÷ 7000 ÷ d²

BHNmin = SD × mv² ÷ √bl ÷ 16,000

Give that a try with any other results for maximum good accuracy velocity you have and see if comes close? I would be interested to hear how far off it gets?.

Nick,
Thank you for your input. I have felt that bullet "stack up" (your columnar pressure reference) was the most logical explanation with the force on the back of a heavier bullet for the caliber being greater as in your very good explanation.

Thank you for working out your formula. I did put it into an Excel spreadsheet and, as you indicated, the b.h.n.'s are very close in the examples I referenced.

I then tried a 170 gr. .30 caliber bullet @ 2,200 f.p.s. and the b.h.n. came out to 13.9. In my experience, a bullet of at least 18 b.h.n. is required for trouble free shooting over many rounds....but that is in a .30-30 / 22" / 788 /10" twist at about 36,000 p.s.i. Now, perhaps in a .30-06, which will reach that velocity at lower pressure, the 13.9 b.h.n. might work in a slower twist barrel. Based on that, it would seem that pressure, as you mentioned, would need to be part of the equation, and.....perhaps, the barrel twist as well (?).

Thank you again,
John

John,

It's all fun to me. Unfortunately it does seem there is no escaping knowing the peak pressure. We also haven't tried accounting for differing bore surface roughness. So, how much added hardness is needed to accommodate the worst case for roughness is unknown, too?

Uncle Nick,

"Its all fun to me." Me too! There are variables to be sure. At this point I guess that it is trial and error or, in other words, research and development. :)

Thank you for your input.
John