Averaging Brinell numbers for mixing alloys?

[Rangerone]

Hello to you all,

I am contemplating trying a more mathematical way of hitting a particular mix hardness, but I'm sure my idea has been tried before and either embraced or abandoned, but I have searched and found nothing...

I have a CabineTree lead tester and I believe I have reached the point where my repeatability is consistent, meaning that I have a technique which gives me consistent Brinell numbers. With that consistency in mind, my question is this...

Let's say I want to create a mix, and end up with a Brinell number of 10. Could I mix 5 pounds of Lyman No.2 (Brinell number of 15), and 5 pounds of pure lead (Brinell number of 5) and then end up with something very close to a Brinell number of 10?

I know I can try this and just test the results, but I did want to go through lots of mixing if the end result was going to be inconsistent, and I'm sure that someone here has tried the same thing.

What I have done in the past was to keep the tester bolted down to the end of my melt bench and simply pour off a few ingots, toss them on the floor to cool and then test them. At the same time, I would throw a couple of them into a bucket of water and test them as well. I have never been as consistent as I wanted to be, so I am looking for alternatives.

When I am smelting down scrap lead or whatever lead I have scrounged from other sources, I keep a set of numerical, metal stamps nearby and I test a few ingots and then mark the entire lot/mix with the correct Brinell number. I have accumulated several thousand pounds of smelted lead in various hardness's, so I am trying to find a simpler and more consistent way of mixing.

Your opinions please... And thank you!

[ANeat]

For the different alloys it really depends on what is in it to get the BHN. Tin, Antimony, something else.

Will a tin/lead alloy at 10 bhn and a Lead/antimony alloy at 10bhn mixed together result in a 10bhn alloy???

Honestly I dont know, I worry about bullet fit primarily and hardness only if necessary.


When I want to make up a batch of bullets I have a general idea of the final application and try to get something in the required hardness from mine and everyone elses past experience.

If I need something around 10bhn I do my best and mix up a batch, usually 100 pounds; and if its 10bhn great, if its 8bhn, or 12bhn, thats great as well..... If the bullets cast to the size needed

[lylejb]

I know I've seen threads here about this, and the bottom line was hardness was not a linear function.

[rob45]

Well, the "add then average" formula has been used for quite a while, but some recent (and many not so recent) findings indicate severe inaccuracies in the method.

As an example, take your 1:1 ratio of Lyman No.2 with pure lead.
Using the method to which you refer: (1#x15 BHN + 1#x5 BHN) / 2# = 10 BHN

But if the lead is truly pure lead, and the Lyman No.2 truly has a composition of 5/5/90, combining them in equal amounts does not give us 10 BHN as the formula suggests. It gives a BHN very close to 11.5

So sometimes the averaging method gets us close, and other times it's significantly inaccurate.

When mixing two (or more) unknowns, the method could be used as a starting guideline, expecting nothing more than a rough estimate.
So the best case scenario is to use the formula to make a small batch, then observe how close it is to your target BHN.
If the result is harder than your target BHN, make another small batch using less of the harder component, and retest.
If the result is softer than your target BHN, the next batch needs more of the harder component.

Detailed notes are mandatory when doing this so as not to forget the amounts of each required when you do reach your target. Plus, if you later need a different BHN, you have a record of your previous attempts for reference.



What I have done in the past was to keep the tester bolted down to the end of my melt bench and simply pour off a few ingots, toss them on the floor to cool and then test them. At the same time, I would throw a couple of them into a bucket of water and test them as well. I have never been as consistent as I wanted to be, so I am looking for alternatives.I might add that consistency in your hardness testing is very important, not only in your application of testing, but also when you test. A majority of alloys will age harden to some degree, so keep that in mind. I prefer to wait at least a week before testing for hardness.

[montana_charlie]

Let's say I want to create a mix, and end up with a Brinell number of 10. Could I mix 5 pounds of Lyman No.2 (Brinell number of 15), and 5 pounds of pure lead (Brinell number of 5) and then end up with something very close to a Brinell number of 10?
When you say "let's say" that's kinda like saying, "let's pretend"...

So, let's pretend that the numbers in your example describe an alloy you actually want to find...and let's pretend that you really do prefer to use Lyman#2 and pure lead to get there.

Dan Theodore is known to many in the BPCR community as a avid experimentor who works scientifically to find answers. As it happens, he just completed a year-long trial to find out how alloy hardness varies over time.

One of the alloys he tested is one he calls his 'three-seven alloy'. It is 97/1.5/1.5, and is made by combining three parts Lyman #2 with seven parts pure lead.
It turned out to be an exceptionally stable alloy. It was 8.2 BHN when cast, but increased to full hardness after 18 hours. It then remained at that hardness for the remainder of the year-long test.

Dan tests alloys with the Lee hardness tester, but also used the Cabine Tree unit for comparison. He feels the two agree pretty well.

Of specific interest to you will be the news that Dan's three-seven alloy stabilizes at 9.8 BHN.

Izzat kloss enuff?

CM

[Barnowl]

Rangerone,

See this thread for discussion and an Excel spreadsheet that will do what you want.

http://castboolits.gunloads.com/showthread.php?t=67401&page=2

Kevin

[JesseCJC]

Since I was going to ask something similar I will just post here and hope not to hijack as it pertains to finding the right BN hardness.

What would be a good ratio of clip on wheel weights to the stick on? Should I keep the stickies all to themselves and add in some solder or just mix them in a correct ratio with the clip ons. Or hell, should I just throw it all in the same pot?

Shooting out of a 45acp Glock if it matters, thanks.

[Echo]

For the .45, throw them all together. You might find that you need a little added tin for mold fill-out, but the .45 is very forgiving re alloy. My own (limited) experience is that all stickies are NOT pure Pb - some seem to be about the same as clippies. YMMV.

[Rangerone]

One of the alloys he tested is one he calls his 'three-seven alloy'. It is 97/1.5/1.5, and is made by combining three parts Lyman #2 with seven parts pure lead.
It turned out to be an exceptionally stable alloy. It was 8.2 BHN when cast, but increased to full hardness after 18 hours. It then remained at that hardness for the remainder of the year-long test.

Dan tests alloys with the Lee hardness tester, but also used the Cabine Tree unit for comparison. He feels the two agree pretty well.

Of specific interest to you will be the news that Dan's three-seven alloy stabilizes at 9.8 BHN.

Izzat kloss enuff?

CM

I appreciate the recipe, I will try it next week.

[Rangerone]

Well, the "add then average" formula has been used for quite a while, but some recent (and many not so recent) findings indicate severe inaccuracies in the method.

As an example, take your 1:1 ratio of Lyman No.2 with pure lead.
Using the method to which you refer: (1#x15 BHN + 1#x5 BHN) / 2# = 10 BHN

But if the lead is truly pure lead, and the Lyman No.2 truly has a composition of 5/5/90, combining them in equal amounts does not give us 10 BHN as the formula suggests. It gives a BHN very close to 11.5

So sometimes the averaging method gets us close, and other times it's significantly inaccurate.

When mixing two (or more) unknowns, the method could be used as a starting guideline, expecting nothing more than a rough estimate.
So the best case scenario is to use the formula to make a small batch, then observe how close it is to your target BHN.
If the result is harder than your target BHN, make another small batch using less of the harder component, and retest.
If the result is softer than your target BHN, the next batch needs more of the harder component.

Detailed notes are mandatory when doing this so as not to forget the amounts of each required when you do reach your target. Plus, if you later need a different BHN, you have a record of your previous attempts for reference.


I might add that consistency in your hardness testing is very important, not only in your application of testing, but also when you test. A majority of alloys will age harden to some degree, so keep that in mind. I prefer to wait at least a week before testing for hardness.

I appreciate this, and I always keep meticulous notes so that I can return to the same place. I realize that everything we do starts off as a rough estimate and then we massage it a bit from there. While I do enjoy this hobby, I'm not interested in spending hours getting to the right mix, when I can instead be productive and casting lots of bullets.

I have modified my Cabine tester so that it is more consistent then originally supplied. And, my technique is such that I can test 10 bullets in a row and come up with measurements within less than .002 across the 10. I then modify the mix from there, knowing that it will change a bit over the next few days.

Thanks for all the comments...

[Lead pot]

Rangerone.

When making a big batch of alloy like your 100 pounds it is tough to get even BHN numbers through out that whole batch unless you spend a lot of time mixing and fluxing the alloy and even then there will be pockets in that batch kind of like mixing pancake batter and have lumps in it, that might be light or heavy on lead or the other stuff Tin/Antimony that wont attach to the lead. Lead don't absorb the tin/Antimony that stuff clings to the lead and if you over heat the mix when you cast your bullets and you see the frosting, well that is the tin and antimony coming to the surface. Kinda like galvanizing on sheet metal.
I used to make big batches like your doing but I cut it down to just 40 pounds and I found that it is more consistent and I use a lot of rosin to flux the mix and I mark the batches and only use it when I cast. The variances in the alloy hardness I think effects the bullet performance more then the weight say three grains difference as long as you dont have voids or a bad fill.

Kurt

[Adam10mm]

Man, I used to get all worked up over alloys, BHN, etc. Then I got lazy. Mix what you have and shoot it. If it doesn't lead, go on with life. even a 2-3 BHN variance isn't the end of the world.