Confused about alloys

[Traffer]

Hi Folks,
I am trying to figure out the alloys for bullet making. According to Rotometals, each % of Antimony adds .92%, so 5 + (.92 * 7.5) = 11.9-Brinell, and each % of Tin adds .3 to the Brinell rating.
I just bought some 7.5% antimony 92.5% lead alloy that is according to Rotometals formula is 11.9bhn. My tests show it to be about that also. I am curious about alloys like Lymans #2 which is 5% tin 5% antimony and 90% lead that is about 16.5 bhn. According to Rotometals formula that would make Lymans #2, 10.1bhn. So if I added say 5% tin to my 7.5% antimony 92.5% lead alloy would that take it considerably above 16 or 17bhn? or will it be 12.5bhn as the Rotometals formula would suggest. I am just learning this stuff. I am under the impression that for a 9mm medium load I would want at least 15bhn. Is that incorrect also? I came up with that number by applying a formula to the pressure and base size of a 9mm. I truly am confused here.

[HangFireW8]

Tin hardness falls off quickly after the first 2%.

[dragon813gt]

Read this multiple times until you have a good understanding of the basics: http://www.lasc.us/Fryxell_Book_Contents.htm

And don't get to hung up on BHN. I've never even looked at one of the pressure vs. BHN charts.

[NyFirefighter357]

Download the alloy calculator & play with it. http://castboolits.gunloads.com/show...oy-calculators

[Traffer]

Thanks Dragon,
This is a very good read. In 10 minutes of reading so far I have learned more then I knew previously. Very very good indeed. I am really liking the idea of getting the alloys worked out cheaply and effectively with heat treating and water quenching.

Read this multiple times until you have a good understanding of the basics: http://www.lasc.us/Fryxell_Book_Contents.htm

And don't get to hung up on BHN. I've never even looked at one of the pressure vs. BHN charts.

[Traffer]

I just found something very interesting on the hardness calculator. In the notes he says that Rotometals use this formula:

Estimated hardness calculated by Rotometals formula: Brinell = 8.60 + ( 0.29 * %Tin ) + ( 0.92 * %Antimony ) Another person wrott the same formula but instead of starting with 8.60, They started with 5 as in pure lead is 5bhn. This is how it was stated:Pure lead is 5-Brinell. According to Rotometals, each % of Antimony adds .92%, so 5 + (.92 * 7.5) = 11.9-Brinell. One of these is wrong. I input 7.5% antimony and 92.5% lead and the calculator gave a brinell number of 16. So my question is: IS 7.5% ANTIMONY AND 92.5% LEAD 11.9 BRINELL OR 16 BRINELL. SOMEBODY SHOULD BE ABLE TO GIVE ME A DEFINITIVE ANSWER TO THIS

Download the alloy calculator & play with it. http://castboolits.gunloads.com/show...oy-calculators

[imashooter2]

The definitive answer is that there is no general agreement on formulas for calculating hardness.

[Traffer]

So there is no difference between 11.9bhn and 16bhn. I know it is not exact but that is a big discrepancy.

[dragon813gt]

You are really over thinking things. I cast for everything w/ the same alloy. Starts out around 11bhn. If I need it harder I water drop it. No clue what it ends up but it works. There are a lot of other aspects to focus on that are more important than hardness.

[toallmy]

I have found the 9mm to not be picky about hardness at moderate loads . Fit to bore is much more critical , I have used soft plumbers with very little tin . As long as you can get it into the case without sizing it under bore you are fine . I can't help you with the hardness you are looking for but you can use what you have , and only add as much tin as you need to get good fill out on your boollits . I let over thinking casting stop me from doing it for years so now I just do it . Cook some up and try em.

[OS OK]

Just study the book, it's definitive. All you need to add to the book is a little experience casting and shooting your product. If you don't understand what is happening, that is, if you don't understand what the book tells you...how in the world will you make intelligent decisions in adjusting your blends of boolit metal or in sizing or lubing or diagnosing problems of leading the barrel or lube that doesn't work? Many things work in concert to get that slug on the 'X' downrange.

Don't shy away from the facts...keep reading and applying what you have learned, you have a grasp of the numbers alright, just keep at it.

OS OK

[imashooter2]

So there is no difference between 11.9bhn and 16bhn. I know it is not exact but that is a big discrepancy.

No, the difference between 11.9 bhn and 16 bhn is 4.1 bhn. Those are absolutes. There is no general agreement on formulas to calculate how much of what metal added to an alloy will produce 11.9 or 16 bhn.

Dragon813gt has given solid advice. Casting is as much art as science.

[Traffer]

There have been two considerations for my questions here. One is to get a handle on casting for 9mm. The other is very important to me. I purchased a box of lead that is supposed to be 7.5% antimony. I tested the hardness and it came out to be just over 11bhn. To me that does not seem right. As in, does this really have 7.5% antimony? or is it range scrap? Now someone here said that the rotometals formula is 5+ (.92 x the percentage of antimony) I have read in another place that the formula is 8.6+ (.92 x the percentage of antimony). Using the first formula would indeed put 7.5% antimony lead at 11.9bhn. The second one would put it at 16bhn which I would think is the correct one. Again my question is about did I actually get what I paid for or did I buy range scrap. I do appreciate all the input and have learned a lot here. Indeed if I had known that I could harden the lead that I already had before buying the (7.5% antimony) lead, I wouldn't have even bought it. I can just water drop the wheel weight lead to get the hardness I want.

[MrWolf]

I have never done it but many say to take wha you purchased to a scrap yard with an analyzer gun. This way you know exactly what you bought. Think a member or two also have access to one.

[dragon813gt]

Unless you bought the lead from a foundry, like Rotometals, it's anyones guess as to what it really is. Most people are honest. 9mm is one of the tougher cartridges to cast for. But most of the issues can be fixed w/ proper sizing and lube. You don't need really hard lead. Straight WWs will work. I water drop almost everything for ease of handling.

[OS OK]

The stuff that we use for soft lead varies from 5-8.5 BHN or thereabout...God only knows what the roof flashing mfgr.'s use to make that product...so long as it is soft enough to conform to chimneys and the like it gets the job done.
I had dive weights left over from years ago when the wife and I used to dive...they said that they were soft lead too but they measured anywhere from 7.5 to 11...well that's sorta soft. Roto Metals is in the lead business and have means of identifying their metal more specifically and can figure using the math more accurately because of that. We can't just assume that all soft lead is the same.
The alloy calculator allows us to use various sources of lead that has taken this into consideration and it works fairly well as long as we do our part and accurately weigh and measure our blends.
Last time I used it to blend roof flashing and Linotype I expected to get 12.5 and actually got 13.5 BHN, that's close enough for me, I'm happy with that.
Also if there is any small percentage of arsenic in the lead that makes it even more productive in hardness treating by water dropping...who knows about that content unless you go to a scrap metals dealer and get them to test with their instrumentation?

Here's another interesting read... https://www.scribd.com/doc/49162427/...ner-and-expert

[Dusty Bannister]

The information on various lead mixes or alloys are based upon specific formulas. Is there any question that Linotype has a specific ratio of component metals? The various alloys and mixes and their hardness readings are well documented in the cast bullet manuals.

The OP gets off track when not realizing that the Rotometals guideline is used to ADJUST the unknown alloys we commonly use. To adjust the hardness of lead alloys, not to build them.

[OS OK]

qwerwqweweweewewed

My apologies fellas...I just went to the kitchen to clean my wireless keyboard...came back to the screen all scrambled!

This was not a voluntary reply to Dusty or anyone else...I had the thought of taking the batteries out and didn't...guess that I should have listened to that little voice I so regularly ignore...big mistake...here's proof!

charlie

[Dusty Bannister]

Certainly no harm, other than sore from laughing. That might be the best one of the day.

[OS OK]

A little levity goes a long way! It's just a little embarrassing though being the butt of the joke.

charlie