Age-softening Age-hardening I'm confused! :-S

[Beaverhunter2]

I've read in several places about air-cooled boolits "age hardening". In other places I've read about water-cooled boolits "age-softening".

If this is true, would it be safe to assume that you could cast which ever way you prefer, let the boolits sit for X days/months/years and the hardness would be consistent with the "base" hardness of your alloy? Also, does anyone know how long it would take for boolits to reach equilibrium?

This casting business is quite a learning experience! :-D

Thanks for any insight!

John

[grumpy one]

I've read in several places about air-cooled boolits "age hardening". In other places I've read about water-cooled boolits "age-softening".

If this is true, would it be safe to assume that you could cast which ever way you prefer, let the boolits sit for X days/months/years and the hardness would be consistent with the "base" hardness of your alloy? Also, does anyone know how long it would take for boolits to reach equilibrium?

This casting business is quite a learning experience! :-D

Thanks for any insight!

John

John, age hardening and age softening are separate processes that happen simultaneously. Age softening, however, only happens if there has been a physical intervention to create temporary hardening. So, if you cast into a hot mould and air cool the bullet, precipitation hardening (due to the lower solubility of antimony at room temperature compared with at melting temperature) will occur over a period of at least a year, but at a negatively-accelerated exponential rate; most of the hardening will happen in the first couple of weeks. However if you quench the casting while it is still hot, the lead matrix will solidify while relatively little of the antimony has crystallized. A much larger amount of antimony will then have to force its way into a fully cooled lead matrix than if cooling had been more gradual. This will pre-stress the lead matrix to a greater extent, which manifests itself as additional hardness. However lead is very prone to creep, or stress-relaxation by slippage. The additional hardness will therefore tend to decay exponentially as slippage occurs.

[Ricochet]

Different alloys (and likely, same alloys differently treated) will age harden and age soften at different rates. In my 60 year old Metals Handbook there are some tables showing several type metal alloys' hardness immediately after chill casting, then, with and without a 2 hour heating to about 200°F, how they hardened to peak over about 6 days and over about 6 months got a little softer than peak hardness. I once laboriously typed the whole mess and posted it on this board. I'm too lazy to hunt it up now.

Alloys with lesser precipitating element content will harden more slowly. The Metals Handbook says that 1% antimonial lead doesn't stabilize in hardness for a year or so.

Surely over geological time they'll all end up equilibrated, but it sure doesn't happen in 8 years because I have water dropped boolits I cast that long ago, and they're still quite hard.

[JohnH]

I certainly don't mean any of this to take wind from your sails, but for me, these days I chalk this up to minuta. There is a lot in lead metalurgy that is just that.... minuta. For most of our needs this kind of knowledge is nice and can lead to great conversations, once in a while it's actually useful ;) Yet it often has little impact on our day in day out shooting. I've tested hardness on bullets I cast a year after, no change in either hardness or in how they shot. If you are holding cast boolits so long that the effects of age hardening or softening affects your loads..... either you aint shootzen enough, or you're castin' too much.

As a general rule, most lead/ tin/ antimony alloys that are air cooled will need a few days, maybe even a week or so to reach full hardness. But what you are doing with the alloy matters as much, perhaps more.

At pistol velocities of 700-900 fps, I've never had trouble with leading, even when I shot bullets within 4 hours of casting. Presently I'm shooting half WW and half Linotype. No other reason than the material is on hand and makes a good alloy for my shooting needs. It typically reaches 17 BHN in 30 or so hours. Yet I've driven it 1700 fps within 12 hours of casting, no leading...was about 14 BHN. Barrel condition has as much perhaps more to do with how a cast boolit performs as it's hardness.

In another post, you made reference that you're new to this. That's a good thing! Listen, learn ask questions, learn some more, but keep this in mind.....Casting bullets, loading and shooting them is actually quite forgiving. It may take a bit to work out the kinks in your techniques and methods, but in the end quite useable and enjoyable results come rather naturally.

I started casting in part as a result of meeting my wife's uncle. He had been casting at least 30 years at the time we met and we never talked of such things as this. Being quzzical, I spent the next twenty years reading all I could find on the subject of casting. I've pretty well come around to my uncle's persuation....if it'll pour, it'll prolly shoot.

[Ricochet]

For all that I like to delve into the theory of this stuff, I actually work on JohnH's wife's uncle's operating principles. I don't own a lead hardness tester and use the crudest sorts of methods to compare hardness of alloys. I don't use any well characterized or repeatable alloy compositions. If it pours, it can probably be made to shoot.
:mrgreen:

[TCLouis]

measurement technique. it is based on the third hormonic of G sharp.
In common terms I call it the "Ring", "Thud" Technique.


the technique require specialized ingot molds that are shaped and sized to allow the ingots to perform as required to test hardness with a repeatablity to 3 decimal places.

First the alloys must be done in batches of 3-400 pounds and require the use of a specialized organic based flux and will only work with the entire mixture is melted with lignin base fuel.

Properly done it takes some time to prepare, but I will attempt to make short the whole procedure.

First I prop my melting vessel ( 1/2 of a 10 Gallon Water heater tank ( lengthwise cut) on some rocks and fill the tank to the brim with wheel weight as and whatever lead I think will make a mixture good enough to send down range (300-400 pounds takes a while to send down range a few hundred grains at a time (owning several 45-70s and 54 ML will speed the process)) I then fill the rest of the space in the tank with sawdust and used motor oil.

Now imagine scrap lumber and tree limbs piled over this until it resembles a Viking Funeral Pyre.

Torch it off and walk away for about an hour.

Skim off the surface materials which will be WW clips, trash and carbon from the sawdust. The carbon does an admirable job of protecting the surface of the lead from oxidation.

Now it is time to don full face shield, long sleeves, heavy welders gloves and a long handled 10 pound ladle (1 quart sauce pan with long rebar handle attached works very well for this)

Now for the molds . . .
1 1/2 X 1 1/2 X 1/8 angle iron welded into gangs of 4 with a divider at about 4" will be filled MANY times before the casting session is over, but make ingots that average 1 pound. Those triangular ingots sure do stack into a neat stable stack. Imagine how the trianglular cross sections will go together and one can see a nice neat flat pile, They also fit very neatly into a Lee 20 pound pot.

Now for the hardness testing that I said I would ultimately get to . . .

Hit two of the ingots together and if the resulting sound is "thud", it is fairly pure lead, slight ring and it is WW hardness or so and distinct ring and it is up in the Lino category.

As one can imagine I do not have to do this but every couple of years.

And thus the highly scientific "Ring", " Thud" hardness testing method was developed.

Slight ring method will be an alloy that will allow 105 rounds of C311316s lubed with NRA 50/50 to leave a 30 Herrett barrel at 2105 FPS in one afternoon session with NO leading.

[randyrat]

Hay, don't knock it.... it works; Thud, Ding, Ring, Ting, Providing you don't have war torn ear drums. So far i'm able to hear the difference.....

[Beaverhunter2]

Whew! Thanks for all the info, guys! I sure am learning a lot!

I'm a lot like Ricochet- I like to read all the good stuff on my favorite hobbies. Then I apply what I've learned as long as it doesn't require too much $ or too many headaches. For example:

I just finished "shortening" my Lee TL314-90SC mould. It was casting at 91 gr, now it's at 78. I'm hoping it will perform better in my Guardian .32. Now I'm also thinking about lapping out one of the cavities to fit my .32 BP squirrel rifle. The rifle's twist is 1-48 and it won't stabilize maxi-balls. The maxi-balls are .635" long and 78gr TL is .495, The 78 gr boolit is currently .316 AC. Any recommendations on an as-cast diameter? (Remember, I need to be able to shove it down the barrel without deformation.) Thanks again for all the help!

John

[Maximilian225]

As a general rule, most lead/ tin/ antimony alloys that are air cooled will need a few days, maybe even a week or so to reach full hardness. But what you are doing with the alloy matters as much, perhaps more.



Is there any change in the overall size from, say 20 min after casting to full hardness?
Or is it so small as to be almost immeasurable?

[JohnH]

Is there any change in the overall size from, say 20 min after casting to full hardness?
Or is it so small as to be almost immeasurable?

Well, it's like this.... My mic's only read to the thousandth, not to ten thousandths, so I doubt I've accurate enough instruments to be able to sort the difference between the diameters from naturally occuring "rythmes" of casting and the differences occuring as a result of hardness, so I've never done a test. Nor have I ever been able to tell that one thousandth in diameter is the difference between "shoots" and "won't shoot" though I've heard some claim that. That doesn't mean their experience is false, just that I ain't seen it in a way that convinces me that the difference between an accurate load and lousy is .001

Not to get long winded or hijack the thread, but just what kind of comparisons are we making when we start to talk about hardness/softness aging and such? I don't expect ANY load in a revolver to shoot better than 2" at 12 yards when I'm standing on my hind feet. I simply can;t shoot better than that. And I sure ain't going to sit down on a bench and develop a load for a revolver that I'm gonna shoot offhand.....What is the point of that?

Conversly, I shoot mostly off the bench when I'm shooting my rilfes. Not nearly so much for accuracy but rather the rythme of loading, settling in, sighting, breathing, relaxing, firing is in itself a relaxation I seek. Then comes my desire for accuracy. If a load will put 90-95% of the shots into 1 1/2" from 75 yards, I'm happy. Those are my standards. Others seek an entirely higher level of performance, and I'm sure have different standards for their alloy, bullet diameters, runout, hardness, etc.

Again, learn all you can, but keep an eye to your real needs and goals. I do not sort by weight unless I am trying to discern the why whats and whens of a mold giving trouble. Once corrected, I cast and shoot, sorting only by visual defects, as I am lubing the boolits. A good method for a shooter that is most interested in relaxing. Not a method that will work for a competition shooter at all.

A couple years back I had a 375 JDJ barrel for my Encore. I shot well over a thousand rounds and 3 differnet boolits, varied hardness, powders, primers, etc. trying to find what and where it would shoot cast. It never shot well, then began shooting worse. I'm sure I drove the guys here nuts talking about my trials and errors with that barrel. I sold it to a fella who shot only jacketed and ended up with a 25-06 barrel that when I do my part at the bench will shoot 1" groups monotonously. It ain't picky about hardness either, and will drive 17 BHN to 2200 fps before the tale tale wisps of gray at the muzzle show up, which speaks more about the lube than the hardness. It does this with the same accuracy I get at 1600 fps. 2000 fps is miserable for accuracy though.

I personally remain convinced that barrel condition in a rifle is as big if not the larger part of how well a barrel will shoot cast, and that forcing cone condition and timing in a revolver is as important as cylinder throat/barrel dimensions.

I was having trouble once with a S&W Model 10. Fella at the range told me my alloy was too hard (I was shooting linotype, the "go to" metal of day in the gun rags) He told me to try some softer metal. I tried some WW cut in half with straight lead, the trouble dissappeared.

I have a Mosin Nagant that when I size to .310 shoots good to 1300 fps. try for anything above that and groups are lousy and the barrel is a mess. Run the boolit through a 314 sizer and shoot the as cast diameter of .312 (the Lee 312-185 is the boolit we are speaking of here) and I've yet to find how fast I can drive it, I've shot at 1900 fps without trouble. Again this is with an alloy of 17 BHN.

In all, soft or hard alloy is just one part of the equation and in only one instance have I seen that to hold the answer to a problem I was having. Fact is I've found guns to be more sensitive to the loads than the alloy.

Sorry for runnig off so long guys,

JohnH