Lead hardness

[Tenbender]

Does water cooled boolits stay hard with age ? Or would a air cooled boolit harden the same with enough age ?
I like to cast lott's of boolits at a time. More than I can shoot in a year or so. I just don't want to drag the equipment out for a hand full.
If I water drop and , lets say I have a 20BHN , will I have a 20BHN next year ? If I air cool a good alloy with a 16 - 18 bhn will that be 16 - 18 next year ?
No use making this any more of a chore than necessary. I know there's more shooter's than me that store up boolits.
Thanks for helping out a greenhorn.

[ejcrist]

I'm definitely no expert in this area but I can say with certainty that binary lead-tin alloys such as 20:1, 30:1, etc. age soften fairly quickly after casting into boolits to the tune of 1-2 BHN; the more tin the more they soften. When I say quickly I mean within hours. A lot of this info I found on the LASC website. I also believe the lead-antimony alloys age harden but I don't know the extent. I like boolits in the 10-12 BHN range like wheel weights, but when I found out one of my favorite alloys, 16:1 softened over time I started considering other alloys since I shoot some boolits up to around 1,500 fps in some of my wheel guns. I'll continue to collect wheel weights since they're still available and reasonably priced but I want to have alternatives in case regulations get to the point to where you can't find lead wheel weights anymore. Also in the meantime I ordered a Cabine Tree lead hardness testers so I can quantify the results of some of my mixture experiments.

[sqlbullet]

Lead hardness was the subect of two different science fair projects at my house over the last 10 years.

In the first, we tested combinations of heat and quench. We were using isotope lead which had been tested by XFR as about 96% lead, 3%antimony and 1% tin. All three values were a few hundredths below stated, and there were traces of a wide variety of other metals. The values were so low as to not be considered relevant.

We found that air cooled, this lead produced an average BHN of 10.5. When water dropped, it average 27, and when heat treated by oven after the fact to 450° they averaged 25. This difference is accounted for by the fact that dropping from the mold the bullets were hotter than when quenched from the oven. We also found there is a direct relationship between the achieved BHN and the bullet temp when it hit the water.

This data was derived from 18 groups of 10 bullets each. The groups were preserved and several years later another child used them to report on your question...the effect over time. The average results of the batches that effectively were air cooled was they hardened to a BHN of 13.5. The average results batches that were quenched was a BHN of 23.

It was interesting to note that the air-cooled batches that were closest to the BHN of 13.5 changed the least as did the quenched batches that were closest to 23 initially.

The conclusion I drew is that air-cooled this alloy will gradually migrate to a hardness of 13.5 and quenched (regardless of oven or water dropped) will migrate to 23.

So, assuming you cast from an alloy similar to 96/3/1, such as COWW, I would say bullets that are quenched and test 20 BHN on casting day will be about 22-23 a year later. Air cooled bullets that test 10.5 on casting day will test 12-13 a year later.

It should be noted that small changes in the composition of the alloy, especially with regard to grain refiners like antimony can produce relatively large changes in these results.

Hope that helps.

[John Boy]

Good article to increase ones knowledge ... http://www.lasc.us/Fryxell_Book_Contents.htm

[Tenbender]

Lead hardness was the subect of two different science fair projects at my house over the last 10 years.

In the first, we tested combinations of heat and quench. We were using isotope lead which had been tested by XFR as about 96% lead, 3%antimony and 1% tin. All three values were a few hundredths below stated, and there were traces of a wide variety of other metals. The values were so low as to not be considered relevant.

We found that air cooled, this lead produced an average BHN of 10.5. When water dropped, it average 27, and when heat treated by oven after the fact to 450° they averaged 25. This difference is accounted for by the fact that dropping from the mold the bullets were hotter than when quenched from the oven. We also found there is a direct relationship between the achieved BHN and the bullet temp when it hit the water.

This data was derived from 18 groups of 10 bullets each. The groups were preserved and several years later another child used them to report on your question...the effect over time. The average results of the batches that effectively were air cooled was they hardened to a BHN of 13.5. The average results batches that were quenched was a BHN of 23.

It was interesting to note that the air-cooled batches that were closest to the BHN of 13.5 changed the least as did the quenched batches that were closest to 23 initially.

The conclusion I drew is that air-cooled this alloy will gradually migrate to a hardness of 13.5 and quenched (regardless of oven or water dropped) will migrate to 23.

So, assuming you cast from an alloy similar to 96/3/1, such as COWW, I would say bullets that are quenched and test 20 BHN on casting day will be about 22-23 a year later. Air cooled bullets that test 10.5 on casting day will test 12-13 a year later.

It should be noted that small changes in the composition of the alloy, especially with regard to grain refiners like antimony can produce relatively large changes in these results.

Hope that helps.

Thanks. You answered my question. My way of looking at casting ,if the boolits would be stored, mix a alloy just under the desired BHN and let nature take it's course. Like I said. I don't want to fire up the pot every time I need boolits. I will make them up , size and store. Lube them when I need them.

[David2011]

Tenbender,

Just curious; what are you casting? Do they need to be really hard?

Alloys with significant amounts of antimony will age harden for a while after casting. It's really noticeable if you put off sizing for a couple of weeks compared to sizing fresh boolits. So far (since the early '80s) I've only cast for pistols so hardness hasn't been the issue it is with higher velocity rifle boolits.

This chart will help determine how hard boolits need to be based on the pressure they experience.
http://leeprecision.com/cgi-data/instruct/90924.pdf
Just look at the maximum pressure you expect and follow back to the bhn column to see how hard to make the boolits.
Standard full loads of 45 Colt at 14,000 psi = bhn of 11.0 or so. COWW+ some tin, 1.5% to 2% and you're good.
Full bore .44 Magnum at 36,00 psi = bhn of about 28. Straight linotype is only around 22 but it has held up ok for me at hotter loads than this. In a 14" Contender I'm chrono'ing at 1600 fps and the boolits work well. Straight lino, air cooled, held together from the right shoulder exiting the left ham of a 200 pound feral hog.

I have some straight lino 250KTs that are 5 or 6 years old. I mode up about 125 rounds and with the very substantial recoil (within specs for Ruger and Contender only loads) they have lasted a while. I'll test the hardness and report back. IMO it would be better to add some tin and coww or sow and water drop to get the hardness up and have a more ductile boolit rather than cast from straight lino.

I hope this is helpful.

David

[Tar Heel]

Good article to increase ones knowledge ... http://www.lasc.us/Fryxell_Book_Contents.htm

Ditto on the above ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[Tenbender]

David, I'm casting fot a 45 Colt carbine, 7X30 Waters Contender pistol and a 30 30 carbine. All I'm after is a boolit I can punch paper and hunt with as well. 14 - 16 bhn will do everything I want as I see it. If I'm wrong let me know. I do cast 40 S&W's but a 10 or 11 will be fine for that.
Later on in my quest I might cast for a 308 but not at this time.

[454PB]

Way back in 1981 I got on a casting spree and cast 100 pounds of COWW into uncle Elmer's 452424 SWC. I water dropped these, stored them in pipe tobacco cans, and shoved them under the loading bench. Fast forward 30 years, I decided to do some hardness testing on these stored boolits. When the where cast, I had no hardness tester, but they now measure 18 BHN.

[montana_charlie]

Lead hardness was the subect of two different science fair projects at my house over the last 10 years.
What do you use to test hardness?

CM

[David2011]

David, I'm casting fot a 45 Colt carbine, 7X30 Waters Contender pistol and a 30 30 carbine. All I'm after is a boolit I can punch paper and hunt with as well. 14 - 16 bhn will do everything I want as I see it. If I'm wrong let me know. I do cast 40 S&W's but a 10 or 11 will be fine for that.
Later on in my quest I might cast for a 308 but not at this time.

Colt .45 requires a hardness of around 11.0 max per the Lee Lead Hardness Tester chart. The original loads were 30 and then later 40 grains of black powder and a soft lead boolit. That is not a load to sneeze at 40 grains of black. It's plenty stout.

The .30-30 requires hardness in the upper teens to 20 at ordinary cast loads. According to Lee, the BHN should be near 30 to achieve factor velocities in the 2400 fps range. I don't cast for that caliber but it sounds excessively high to me. There are a LOT of members that know everything you need to know about casting for the .30-30.

Lee's chart says the .40 should have a hardness around 23 but you are correct, much softer will work well. My alloy for .40 is 20 pounds of WW and 1/2 pound of monotype. I cast and shot about 50,000 of that alloy without a hardness tester and little to no leading but it worked well even without knowing the hardness. The alloy picks up the machining marks in the mold and has excellent fillout.

I don't shoot the 7x30 Waters but it seems like that's a good candidate for a gas checked boolit which can be softer than a plain based boolit for better terminal performance.

I've shot a gazillion of my own cast pistol boolits but defer to the experts on rifle cartridges.

David

[osteodoc08]

I'm not 100% sold on the hardness calculator that lee puts out. Even in high velocity magnum handgun cartridges I will use a Lyman #2 equivalent with a GC and haven't had any issues. Even out of a 454 Casull which has the pressure behind it. Matter of fact, I used a bunch of the 45 Ruger only 305gr Penta HP made out of ACCOWW with a GC in front of a near max charge of 296 and never had any leading issues and accuracy was better than I could hold.

Ive never ver ventured over to rifle that much but the 30-30 and 32WS loadings have been medium velocity loadings with ACCOWW and never had an issue. Sooooooo, I'm not really sure if from my anecdotal evidence that I've seen first hand myself if these needed BHN really apply if you have good fit and lube.

[osteodoc08]

What do you use to test hardness?

CM

Personally I use a Saeco tester I bought dad 4-5 years ago. Other popular ones out there. A quick search should turn up more reading than you care to read.

[montana_charlie]

Personally I use a Saeco tester I bought dad 4-5 years ago. Other popular ones out there. A quick search should turn up more reading than you care to read.
I am not looking to learn about hardness testers. I want to know which one sqlbullet uses.

CM

[osteodoc08]

I am not looking to learn about hardness testers. I want to know which one sqlbullet uses.

CM

Ah, understood. This is a good question.

[Case Stuffer]

A few points which I find confusing.

To borrow from a great source

http://www.lasc.us/Fryxell_Book_Chapter_3_alloySelectionMetallurgy.ht m

Snip:


Heat treating and water quenching. This age hardening of antimony containing alloys can be accelerated at higher temperatures, i.e. heat treating the bullets. This is most commonly done by sizing the bullets first (since lead alloys work soften, and hence sizing would negate a significant portion of the hardness imparted by the heat treating process) then heating them to about 450° F in the oven and quenching by dumping them in cold water. The hardened bullets are then lubed using the same sizing die that was used before (so that no actual sizing takes place). Done in this manner, bullets cast with an alloy containing 5% antimony, 0.5% tin and 0.17% arsenic, which would normally have a Brinnell hardness of a little over 16 (after aging for 6 days), can be hardened to a BHN of over 35 (see Dennis Marshall‘s chapter “Stronger Bullets with Less Alloying“ in “Cast Bullets” published by the NRA). Notice that this alloy is not tremendously different from the common wheelweight. Much the same sort of result can be obtained by casting with a hot mould and water quenching directly (place a towel over the water bucket with a 4“ slot cut in it to contain the splashes). Mould temperature is critical for maximum effective hardness. Bullets water quenched from a “cool” mould (i.e. one from which the bullets were smooth and shiny) were found to be similar to air-cooled bullets. But bullets dropped from a mould that was “hot” (i.e. hot enough that the bullets were frosty over their entire surface) were found to have BHN of over 30 when water quenched. In a separate study, such a mould was found to have temperature of 430° F, very similar to the optimum oven temperature found in the heat treatment study (ca. 450° F). I don’t normally cast quite this hot, but even so, water-quenching WW alloy routinely gives me bullets with a Brinnell hardness of 18. One of the advantages of hardening bullets in this manner, as opposed to using linotype to make them hard, is that they are tougher and not as likely to shear or fragment on impact.


So how does water quench from mold or from oven work if one turns around and sizes afterward?

Most sources state heat for one hour in oven before quench so how do some seem to get results quenching after only 20 to 30 minutes at 400F while baking power coat and then quenching?

How much does sizing after heat treat reduce hardness and since sized area is powder coated does it really matter?

How do you check the siized / worked area anyway? I use a Saeco Lead Harness Tester on the nose of the Boolit. All hardness tester I am aware of require a flat area to test.
Short snip

One of the advantages of hardening bullets in this manner, as opposed to using linotype to make them hard, is that they are tougher and not as likely to shear or fragment on impact.

Another advantage is that Lino now goes for $3 per pound or $2 if you purchase a thousand pounds or more so there could be a large cost savings.

[Yodogsandman]

"Most sources state heat for one hour in oven before quench so how do some seem to get results quenching after only 20 to 30 minutes at 400F while baking power coat and then quenching?"-Case Stuffer

Note that quenching after curing PC is mostly done just to cool the boolits faster. Most sources still say to thoroughly heat for at least an hour to heat treat boolits. That also goes for PC'd boolits. Most will size boolits prior to oven heat treating and/or very soon after if water dropping from the mold. With PC, I size before HT'ing, HT, then PC and quench in one session. I then re-size after PC/quenching as soon as possible.

Expect the cured plastic powder coating shell to be about 26-28 BHN alone.

Work softening by sizing is not noticeable. The HT'd boolits are hardened all the way through and the very little surface area that's disturbed by sizing isn't a big deal.

[Case Stuffer]

Snip


Heat treating and water quenching. This age hardening of antimony containing alloys can be accelerated at higher temperatures, i.e. heat treating the bullets. This is most commonly done by sizing the bullets first (since lead alloys work soften, and hence sizing would negate a significant portion of the hardness imparted by the heat treating process) then heating them to about 450° F in the oven and quenching by dumping them in cold water


How do you size before heat treating as non lubed Boolits do not size well and any lubication will cause issues with the powder coating.

[Yodogsandman]

Boolits are easy to size prior to HT'ing, there's no extra resistance from high BHN's or GC seating. I size prior to PC'ing with clean tools and the same when sizing after PC'ing. I clean my sizer die and top punch by boiling in water and then drying them off first.

If I plan to lube HT'd boolits, I run them through the sizer die, HT and quench. Then put them back through the same sizer die to lube and seat GC's. Some guys lube after HT'ing with a sizer die that's .001" over sized to prevent any work softening. I just see no difference, maybe others do.