Design and alloy, part II

[fiver]

I know the best medium for stopping bullets is snow.
it slows it down and stops it without really damaging the bullet.

I know that isn't practical but it is an indicator that soft fluffy stuff works better.
if you could get some oats and keep them dry they might make a good medium.

 

[Ian]

Now I'm thinking soft and fluffy for a few feet, then finish off with crumb rubber mulch for the last part. Crumb rubber only distorts soft bullets or bullets going really fast. I can probably get some sawdust if necessary, there are cabinet shops around here still and one might let me raid their dust collector for the asking.

I happen to have enough crumb rubber on hand to make most or all of the trap from that if I don't make it too big (maybe 12" square in cross section), may try that first. Think eight feet would be enough?

 

[fiver]

I would think so.
put some cardboard in about every foot or so and you can see if it is affecting the bullet.

 

[pokute]

Well, I'll toss out one interesting data point. 98-1-1 alloy, as cast, spontaneously age hardens from ~10 - ~20 when allowed to age at room temperature for one year. So, do consider that bullets cast and not fired for several months are potentially very different creatures from those fired within a month of casting.

 

[Ian]

We do. Precipitation-hardening as well as age expansion have bitten pretty much all of us at one time or another. Your statement about the 98-1-1, however, has OWT.

 

[pokute]

This document, which refers to Al alloys, contains a great deal of general info about age hardening. It is public domain.

https://materialsdata.nist.gov/bitstream/handle/11115/189/Metallurgy of Heat Treatment.pdf?sequence=3&isAllowed=y

Here's a patent with some interesting accelerated age hardening data for Pb-Sn-Sb:

https://patents.google.com/patent/US2148741

 

[pokute]

OWT? It's from a peer reviewed journal article that is unfortunately not public domain. Journal Of Power Sources 53 (1995) Pp 45-51

 

[Ian]

98-1-1 physically cannot make 20 bhn without other elements present and some serious heat treating.

 

[pokute]

The units are Vickers. Not the best choice for soft metals, but I *thought* they were close to Brinell numbers at very low values. The data are for the exact alloy. A little more or less Arsenic or Tin and the final hardness drops quite a bit.

 

[pokute]

I apologize if I'm stating the obvious, I just thought that it wouldn't hurt to have some objective sources to "temper" the subjective results that we see based on our less precisely formulated alloys.

 

[fiver]

it's helpful but we gotta keep the numbers in something we all understand.
it doesn't take much stuff to get lead to go from a 5 to a 10, but 20 is really pushing things even with heat.
it would take like 475--500 straight to ice water to get close to 20.

that I don't think is the issue, the issue would be when the bullet is fired, how much stress and pressure from the bottom would a 1/1 alloy take?

 

[pokute]

20 Vickers = 196MPa

if: Pure lead = 5 BHN ( By definition: BHN * 9.8 m/s^2 = MPa) = 49MPa

So 20 Vickers is equal to 20 BHN.

Again, any variation from exactly 98-1-1 shows a dramatic drop in the final hardness. And this is after 400 days of precipitation hardening at 20C, with a laboratory grade alloy. It would be an extremely unlikely result with the kind of metal we work with.

 

[Rick]

it's helpful but we gotta keep the numbers in something we all understand.
it doesn't take much stuff to get lead to go from a 5 to a 10, but 20 is really pushing things even with heat.
it would take like 475--500 straight to ice water to get close to 20.

that I don't think is the issue, the issue would be when the bullet is fired, how much stress and pressure from the bottom would a 1/1 alloy take?

475-480 degrees, right at the slump point of CWW in a pre-heated oven for a minimum of one hour with a minimum 2% Sb alloy will reach 30 BHN in a matter of days. The higher the Sb% the quicker the time curve to age harden. I've done it many times myself. I've also learned that there is little to no need for a 30 BHN bullet, not even in the 454. Typical water quenching from the mold with the same alloy will reach 18 BHN. Can't heat treat the 2% Sb/Pb alloy at 500 degrees. Well ya could but what would be the point in heat treating puddles of lead?

Heat Treating of Lead and Lead Alloys​

98/1/1 alloy to 20 BHN? Vickers? Really?

 

[Ian]

Relevance = 0.

 

[pokute]

Sorry. Guess I misunderstood the original post.

 

[fiver]

help me out here pokute.
I'm missing how this works.

 

[Ian]

Sorry. Guess I misunderstood the original post.

Did you even READ it? Maybe you should. It has nothing to do with copper, aluminum, super-secret squirrel alloy tests, or any of that. Just ternary bullet metal, what properties each bring to the table, what we need to do to accomplish different tasks with our alloy, and how all that plays into dynamic fit. Bottom line, what works for what and why it works.

 

[popper]

H.T. works like this. You have a supersaturated MIXTURE of elements. Air cooled they tend to precipitate into ill-defined 'blobs'. Fast quenching keeps the distribution of supersaturated elements in position so the 'blobs' are not formed (or at least very small). That improves the structure and strength of the material. There are several dual quench methods and one that increases the pressure on the second cycle that REALLY works (6x normal) but WE have no way of any of this stuff. There is actually very little SbSn in the alloy, just globs of Sn & Sb (a & B) of various sizes. Sb/Cu actually forms a molecule that is NOT SbCu but Sb5Cu(?). Sb/Sn 1% will H.T. but not much. Cu/Zn 1% doesn't at all. Yes, I'm speaking of Pb alloys.

 

[pokute]

help me out here pokute.
I'm missing how this works.

I was just trying to provide a scientific basis for what might be observed in the extreme case where the actual composition of the bullet alloy were exactly as stated. It happens that during the development of battery plates, before the introduction of Ca (which the manufacturers did not want to do, because it made reclamation difficult), they tested Pb-Sn-Sb in every possible combination to try to maximize long term strengthening by precipitation hardening. That data included a very surprising result for 98-1-1 that is wayyy outside most people's experience with 98-1-1.

What this implies is that if a group of bullet casters want to share info for the purpose of creating the ultimate bullet for a given purpose, they need to be aware that there is the possibility of wildly different results with seemingly similar alloys. When the alloys are Frankenstein mixtures, the likelihood of repeatability among casters becomes very small.

 

[pokute]

I know from my own experience that being a chemist and metallurgist is little help when casting bullets from scrap of unknown origin. But because I am a chemist and metallurgist, I can appreciate that the results can vary wildly. Anyone here who has ever brewed beer or baked bread knows that things can go wrong in unexpected ways when ingredients are substituted, or of unknown provenance. Getting a consensus on what makes a great bullet is made very difficult by the usually mongrel provenance of our materials. Everybody has a big pile of some random alloy that works for them, but it's different from the next guys.