Alloy question...

[waco]

Most of my cast bullet shooting is done between 800-1900fps. I was given around 200lbs of 22lr lead from an indoor range. It's very dirty. Lots of paper target chunks and carpet fiber?
Anyway. Lots and lots of dross but it does clean up nice. I also have several hundred pounds of Linotype.
What would be a good general purpose mix for my needs? 4:1? Maybe 5:1?
Your thoughts please.

 

[Brad]

5:1 would be a good start point. Could possibly even go 8:1 because it will heat treat if needed.

 

[popper]

boolit alloy
So we have questions, what alloy will work in my gun, for my target, with the terminal effect I want?
Lots of 'info' on forums. High Sb will shatter, hard will lead, soft will lead, etc. What is correct?
So we try lots of 'stuff' to see what works. How do we find an alloy that meets the requirements?
BHN testers measure static stress/strain (force/distortion) Not a direct 'performance' indicator.
Data gleaned from several sources show deformation increases with impact ~50% (over static) with an additional 50% due to temp (0F to 160F). Navy studies show Pb has ~ 1000 psi plastic point - due to impact (from 22ft/sec). Static is about 2K psi.
1800 fps 165gr (0.24#) boolit stops in 0.008 sec (one foot of target). Not realistic, just an assumption as example.
As E=1/2m(v)^2, how does acceleration/deceleration affect alloy. A= d(v)/d(t). = d^2(x)/d(t^2) =F/m
Deceleration = 1800/0.008= -225000 = A = F/m = F/0.24#. So F=225000*0.24 = 54000# or (assume 40cal) 54000/.125=432000 psi. That is peak impact psi.
Deforming the boolit releases energy as does deforming the target. E=0.24/2*1800^2 = 388800. Assume 1/2 in boolit, the rest in target. 63000 calories. So the 165gr goes to 1k F on impact. This answer is NOT true as I just used simple algebra calc. True answer may be 10x lower but this gives an idea of the forces involved. Similar to firing so keeping the pressure down helps.
So we add stuff. Alloy additives Sn/Sb/Cu/As/Zn/S and some others.
I suppose the early guys used whatever would melt and cast. Later we got Pb/Sn, Pb/Sb/Sn of varying amounts. #2, 20:1, 40:1, etc. Generally known 'properties' of the additives; Sb - harder, Sn - better casting, Cu - malleability/hardness, As - faster hardening, Zn - harder, S - harder. So how much of these do we add. What effect does quenching have?
So --- Pb and metals are crystals. Imagine a 2-D grid of dots. You can place another dot on an empty space or substitute a Pb dot with something else. A limit is reached (saturation) when all the substitute/placement dots allowed are filled. If you add more, you get blobs of the replacing stuff. Like the Sb or Sn rich sides of the eutectic curve of #2. IIRC, As = 0.15, Cu = 0.3, Zn,Sb,Sn = 1.5, S = 1 (%wt). But the saturation % is temp. dependent. So the melt can be supersaturated. When we W.D. (quench fast) they are frozen in place. Supersaturated at room temp. When we air cool, we get normal saturation and blobs of the added stuff. We often hear of 'grain-refiners' such as As. Basically doing the same to the other stuff as they do in Pb. Makes the blobs smaller/stronger. These 'additives' also create larger molecules that fit in the dot-matrix and add to the 'hardness'.
So what does this mean?
My general 'rule' - for AC, use no more than room temp. saturation values - except for Sb. It seems to form molecules with almost all the others. I have used Sb/Cu to get BHN up in the high 30s but rock hard is not really needed (unless you want AP boolits). I don't normally see a need or use for Sn. I have been getting good accuracy results with 3-4% (wt) Sb in rifles, more for full fps 308. I am working to find a 'soft' alloy for low fps rifle and pistol. Additives of Zn/Cu/Sb alloy, all at very low %.
I will make one emphatic statement. Leading is not caused by soft or hard alloy per se. Lube failure, gas cutting and land stripping only.
No intention of stepping on LASC articles, we do have more industrial data available now. I don't agree with all their statements. I get tired of the old wives tales about alloys. No expert but been doing a lot of reading in the last couple years. Anyone that has more data, be glad to add. We don't have the Gov. developing this stuff for us.
Waco - doesn't answer your question, just gives an idea what can do what.

 

[Ian]

Deforming the boolit releases energy as does deforming the target.

Yup. When the bullet takes the rifling and gets deformed, the moved metal gets HOT. Like right now. Instant conversion of kinetic to thermal energy. As you said, the alloy (like all metals) weakens as the temperature climbs. Someone way more educated than me could figure this out and put meaningful numbers to it, but smash a bullet with a heavy hammer and note that as soon as struck it is hot enough to burn your finger....also note that the hammer doesn't bounce because the lead soaked up all that energy and converted it to heat. If you do the calculations that F.W. Mann gave us near the end of his tome for a 10-twist .30-caliber, 4-groove, .004" deep grooves, on a bullet with about a quarter inch total bearing length, fired at 2500 fps, you'll come up with about 10,000 psi stress on the engagement points. Small surface area, but the psi is relevant to the strength of the alloy. Plenty for WW alloy, right? Wrong. The most stressed part of the bullet also just became the hottest part of the bullet after being booted through the throat and is streaking along those lands, enduring 10K psi and 2500 fps by the time it reaches the muzzle. Plus it has several tens of K psi and more heat trying to cut past it the whole way. What could go wrong? If it weren't for the barrel holding it together the bullet would splatter like a blob of peanut butter when fired. Pure lead does that when fired with black powder out of short barrels...again Mann did tests and photographed them over 100 years ago. It's amazing that we can manage to shoot lead alloy out of gun barrels at all considering the forces involved...but we do and it's only possible by balancing the components and the forces just so, and even then there are practical limits to what can be achieved. Most cars aren't built to handle a 1G turn on level ground, and some are. They both have four wheels and sprung suspension but just about everything else is different on the ones that can.

So, go easy on the tin if you want to go fast, tin doesn't like abrasion and it makes a sticky bullet alloy. Antimony is great if you don't use more than you need. Better if you choose grain refiners carefully for the job at hand. Create strength when needed through heat treatment rather than creating a stronger "cold" structure which relies on the Sb/Sn matrix. All this is fascinating and fun to learn about for some and maddeningly overcomplicated for most who don't get their kicks by pondering this stuff at two in the morning....Brad already gave the best and most simple answer.

 

[fiver]

4-1 would be close to 50-50 ww alloy, but with more sumthin from the 22 alloy.
there is about 1-1.5% stuff in 22 lead.
I think it's antimony, I have heard it is tin.
the stuff I have worked with comes out fairly shiny and stays that way for quite some time.

 

[popper]

We are like cooks. We know what baking powder, salt, yeast do - but we experiment to find the correct amount for acceptable results. When I started casting I bought #2 as that is what you 'have' to use. Nope, still have 20# under the bench. What we use is a lot like 'mystery' meat. Don't know what it is but add a dash of this and the taste is OK.
Interesting tidbit. Pure lead does work soften!. Navy spent a lot of time & $ to build a test setup for impact testing, to answer a different question. But in the write-up, an off the collar statement - impact strain is 2x the static strain (weakening). Question has been asked about sizing effect on boolits. IMHO it has no effect as the boolit goes through swaging in the bore anyway.

 

[fiver]

and that swaging combined with the associated heat will soften a bullet in the barrel.
I have found in some of my testing that finding a sweet spot for an alloy then hardening it up a bit more can enhance accuracy even further.
at first I attributed it to a slight diameter change making the difference.
then to a structural difference, where the bullet remained closer to it's original shape after the initial damage done getting it to the muzzle.
the odd thing is sometimes Tin is the answer but it has to be balanced by more antimony as well.
going too far is as bad as, or worse than, not having enough.

 

[Rick]

the odd thing is sometimes Tin is the answer but it has to be balanced by more antimony as well.
going too far is as bad as, or worse than, not having enough.

That has been my experience also.
.

 

[popper]

I know my post here may seem silly to you experienced guys but the wives tale I've always heard is 'you got to have tin' for good boolits. Yes, I started that way. Then I asked 'why?". I posted calc. for terminal case only because it's easier to make reasonable assumptions and calc. Another tale is ' fast' powder will melt the base. No, high pressure will weaken the base. So the trick question is how much strength do we loose (for a given alloy) when firing? How much quench hardening do we loose? I did find that my low Sb/Zn/Cu alloy actually quench hardens! Low Sb isn't supposed to do that. Anybody know of a cheap available source of selenium? I know the 'real' answer is on the target but if I keep sending Sb/Sn/Pb down range, I have fun but don't learn anything.

 

[Brad]

My understanding is that tin is used to help make the bullets fill out better. Had nothing to do with improving accuracy beyond having well filled out bullets.

 

[Rick]

Never heard that you have to have Sn for good bullets. Also there are other reasons for adding Sn. It's incorrect that low Sb won't quench harden, of course it will. One of the biggest effects of a low Sb alloy is the time curve for max effect, the lower the Sb the slower the effect.

 

[Brad]

I wonder how much of this is a holdover from olden days when alloys were largely a tin/lead mix? Elmer referred to 16-1 as hard.
Today we use much harder alloys in many cases and usually harden them with antimony, not tin.

I will say that my range scrap in less than 2% Sb and it heat treats nicely into the low 20s. I can add a little monotype and get mid to upper 20s but don't see much need to do so.

 

[fiver]

think of tin in another way besides just allowing the alloy to flow better.
it allows more diameter by breaking through the walls of the alloy letting the antimony/lead to flow through as well this fills out the mold better.
but think of it in terms of it's ability to resist shearing and as a structural booster to the alloy.
when you bend a tin-lead bar you hear it creaking and popping, your actually stressing the tin to it's breaking point and it breaks giving you those noises.
tie the tin to some antimony which helps bind it to the lead even better and in smaller strands and your propping up [kind of splinting] the easily broken down antimony crystals.

it's like taking a piece of particle board and putting a pair of 2x4's on the end.
your running the 2x4's on their weakest plane [won't support 200lbs] and the particle board is junk from the side. [you can just kick right through it]
but put them together and you can support a truck.

 

[Brad]

So we can control, to an extent, the amount of deformation in the throat by altering the tin content? Makes sense to me.
Would be interesting to use a good, known load and rifle combination for a test. If we increase tin by .25% increments and shoot groups how do they change? How much does it take to see a visible difference?

I can see where this would have a big impact on bore riders in particular.

 

[Rick]

Fiver is correct but keep in mind that adding Sn is a good example of too much of a good thing t'ain't necessarily a good thing.

 

[fiver]

it has a huge impact on bore riders.
think about why I use a 4/6 alloy with the rcbs 165 silhouette bullet.
or why I use that same alloy in the AR rifles.
it ain't cause I got a lot of linotype or tin [well not anymore]

you don't want to be getting carried away just throwing tin at the problem.
the majority of my alloys are the same as yours probably somewhere in the 2.5-2.7% antimony range and about 1% total tin.
throwing a bunch of tin at the alloy can hurt you by lowering the melt point or by tin 'coating' [actually small puddles] the surface of the bullet.
like I like to say,,, balance.
a 3-1 ratio of antimony to tin is just about right for most things.
a 2-1 will provide about all the strength and shear toughness you can get.
and a 1-1 ratio works pretty well up to a point [4-5%] then your just not gaining anything, and your not going to get anything from rapid cooling either.

 

[KHornet]

T'aint no magic answer on this one. We tend never to be
satisfied with success!

Paul

 

[Brad]

Ok fiver, that helps clear things up.
All this time I was more concerned with adding Sb to reduce obturation of an alloy. I never thought about Sn as having an effect in a meaningful way.

I have learned something here. Will make me rethink some of the things I have done in the past.

 

[Ian]

That's how I look at tin. Need half a percent or so just because (big difference in wetting quality between half a percent and no percent), but after that it's how much of the Sb percentage do we need to turn into Sb/Sn intermetallic so as to reduce ductility. Sb alone makes lead strong but ductile to a point (yeah about 6% like Fiver said), then past that just incredibly brittle. Sn lets you have your strength, and eat it too so to speak (takes away some of the brittle of high Sb while adding some extra strength and flex), again up to a point and then it starts working against you.

Eutectic alloys like Lino and #2 have their own problems, limitation of heat treatment and lack of abrasion resistance is what I don't like. Heat treatment of Sb alloy is the way to go if you need more strength, or use a step-ladder approach: Push to failure, heat treat, then enrichen the alloy, then start heat treating that to various levels, when you run out of room then enrichen it some more, etc. While you're upping your Sb percentage, go ahead and up the tin. 4:1 is good for low antimony (under 2% Sb) and heat treats like crazy up to about 5-6% Sb. 2:1 is an incredibly versatile Sb/Sn proportion and great for rifles where you need to control the exact heat treatment to maintain both hight strength AND ductility. 1:1 is good for lots of things not requiring heat treat or extreme strength over 15-18 bhn, and if you need ultimate strength heat, go over 1:1, like Taracorp Magnum.....it's good for 50-55K psi launch pressure with a little heat treatment and won't slough off like Lino will above 22-2500 fps.

 

[Brad]

Say I'm using a 2% Sb, .25% Sn alloy. It is heat treated. Think of my new 44 mag bullets and how the lube groove almost entirely went away.
If I added another .5% Sn and heat treated the same would I get a noticeable difference in the appearance of fired bullets? Would the reduced obturation potentially increase accuracy?

I usually would think of adding Sb to reduce the obturation but now can see how Sn, in small percentages, could give the same result.