Boolits increasing in diamter with time

[sleeper1428]

I've been casting boolits for nearly 30 years but this is the first time I've encountered the phenomenon of boolits increasing their diameter after a couple of years of storage. To be specific, a couple of years ago I cast up several hundred 44 cal boolits, both PB and GC style, using Mihec brass moulds, model 432-640 RF in solid configuration (I also have the pins required to make HP boolits but I've noted this problem only with solids since all my HP boolits have already been lubed and sized and seem to have retained their sized diameter). Specifically, the boolits as they dropped from the mould miked, as I recall, between .432 to .433 in diameter, consistent with the diameter marked on the mould. Not having the time or need to lube and size them at that time, I stored them in plastic jars in my garage where the temperature probably varied between 40 degrees F as a low to 80 degrees F as a high. A few days ago I decided to lube and size a few of these boolits and to my surprise, both the GC and PB boolits are now miking at between .434 to .436, making it difficult to size them to even a reasonably large diameter of .432! My alloy is what I've used for years, my own approximation of 'Hard Ball' or 'Taracorp Magnum' alloy - 92/6/2 (Lead/Antimony/Tin). I've made up this alloy in 100 to 200 lb batches so the composition ought to be reasonably consistent from ingot to ingot and as I say, I haven't seen this sort of diameter increase with any other of the boolits I cast for several different calibers (380Auto, 9mm, 38Spl/357Mag, 40S&W/10mm, 44Spl/44Mag, 45Auto, 30-06, 308Win, 7.62X39, 45/70). My melt is PID controlled at between 700-750 degrees F, bottom poured from a Lee 20 pot with the mould preheated on a hot plate, and my boolits in general are just slightly dulled, not heavily frosted as one would expect if the temperature of the melt was too high but also not bright and shiny with incomplete fill as one would expect with too low a casting temperature. Any suggestions as to why this might be happening with this particular boolit would be greatly appreciated.

sleeper1428

[swheeler]

They grow, take your 92-6-2 and add a tiny bit of copper they'll grow even more.

[sleeper1428]

I'm not sure if your answer is intended to imply that my melt may well have had copper in it or if you're simply stating a fact - that adding copper will result in an increase in boolit diameter. If your intention was the former, I'd have to say that in this case you're wrong since I alloyed up the batch from which these boolits were cast - 200 lbs - from pure lead, pulverized antimony and solid bar tin, therefore eliminating the likelihood of having copper contamination. However, if your answer was indeed the latter interpretation, that you were simply stating a fact, then I will certainly agree with you. I will also add that I do not often use pure lead in making up my 'Hard Ball' alloy, old wheelweights being my usual source of lead. But in this case I came into a 'treasure trove' of pure lead and since I already had a good deal of 20:1 and 30:1 already alloyed up and in ingots, I decided to use this new source to create an alloy that was a close to Rotometals 'Hard Ball' as possible. What I tried to make clear was that it appears that this growth in diameter seemed to be limited to this particular mould and I was wondering if anyone else had seen this phenomenon and if so, did they have any explanation for why it occurred.

sleeper1428

[DougGuy]

I knew about age hardening growing the diameter by .0003" ~ .0006" this is fairly common but yours grew excessively! Why I ALWAYS want to size cylinder throats .0005" ~ .0008" over boolit diameter but this is just uncommon for a 44 caliber boolit unless the boolit is quite long. I personally think they shrink in length by contraction internally which pushes them out.

[Whiterabbit]

my boolits do the same. 45 cals. I alloy to close-to-hardball by using a MFRB of WW, SFRB of type, and then I use the xls calculator with the exact weights and alloy I have to give me a sense of how much tin to add to be "close".

It has worked well for me.

Anyways, "this" alloy will exhibit the same issue. What slips through my throats almost too easy become stuck after that. It does take a long long time for that to happen.

They still chamber and shoot well though, even when oversized.

[runfiverun]

antimony does that.
more antimony more growth.

[sleeper1428]

I do understand that antimony does effect the growth (increase in diameter) of boolits but I just haven't seen it occur to this extent in the past. Do those shooters who compete in Cast Bullet Association matches and use linotype (antimony content of 12%) find that their boolits diameters increasing from say .310" to .314" to .316" or even greater after having been stored for a couple of years before being used? If so, I certainly haven't seen anyone making mention of it on either this site or in the CBA Journal. Yes, I would not be surprised by a change in diameter of .0003" to .0005" but to see a change of .003" to .005" was really quite surprising, especially considering that I was using an alloy that I've used for several years and have never seen diameter changes of stored boolits of these dimensions. I did note that Whiterabbit has seen the same sort of changes in 45 cal cast boolits so it seems others have seen the same sort of changes occur in boolits stored for longer periods of time. Considering the fact that I haven't seen such drastic changes in boolits that I've sized and lubed reasonably soon after casting, I suppose the answer is going to be to remelt all the ones that I've had stored for over a year or more and then lube and size them within a month or so of casting before storing them.

[runfiverun]

or store them as made and not size until needed.
that was what I got told By Felix.

I have had bullets sitting around in loaded ammo that suddenly become extremely hard to chamber.
yep they grew, and the nose went from engraving to ENGRAVING.
I had to run the whole batch through and roll crimp them so I could extract them from the chamber.

[Grmps]

from LASC

https://i.imgur.com/QtNXl4E.jpg

[JonB_in_Glencoe]

SNIP...

I stored them in plastic jars in my garage where the temperature probably varied between 40 degrees F as a low to 80 degrees F as a high.

I have no "Specific" metallurgy knowledge in regards to this condition, but I would wonder if the temperature change wouldn't accentuate this issue.

Thinking out loud here:
As the boolit (cast with ternary alloy) ages, the Sb molecules and Sb/Sn molecules go through crystallization and adds to hardness ...and which, I assume causes the growth. I have always understood that air-cooled ternary alloy boolits mostly stabilize (for our purposes) in a couple weeks and surely in a month or so. I wonder if the temperature change could accentuate or stimulate more crystallization over the years?

[JBinMN]

I am not being "snarky", but I have a serious question. Wouldn't this also have an effect on ingots cast with such alloys if left for a long time? Including WW.?

I have used WW that were about 20 years old for casting now & also have cast alloys like 50/50 and 49/49/2 approx. in ingots and marked them accordingly to use later on.

Since it is no different that the alloy used in the boolits and the boolits apparently "grow" ( & hardness?), then wouldn't the ingots do the same over time?

I am sincere in knowing about this. I do not have any control over alloys like WW, but I do over what I choose to make into alloy ingots for future use. I do this not only due to weather , since I cast outside right now, so I want to do the bulk of making ingots outside for use later when I can cast them into boolits inside the small area I am going to use in my garage.

Thanks if anyone can help out with these questions. And Thanks to sleeper1428 for starting the topic. I hope you get your question answered to your satisfaction.
:)

[blackthorn]

JB---I think it would be a pretty safe assumption that ingots made of the same alloy would also grow over time. Unless I am missing something, it does not matter if ingots grow anyway as they will be remelted before casting into bullets, effectively re-starting the whole process. I am kind of curious about your reason for the query?

[JBinMN]

JB---I think it would be a pretty safe assumption that ingots made of the same alloy would also grow over time. Unless I am missing something, it does not matter if ingots grow anyway as they will be remelted before casting into bullets, effectively re-starting the whole process. I am kind of curious about your reason for the query?

it is not so much the "grow" that concerned me, but the"hardness" that may come with the "grow(th)". When I make an alloy I expect it to be a certain hardness when I am done. So, that when I mark the ingot I know what I am getting when I go to cast. If I have an alloy that is supposed to be, lets say, 7-8 BHN when I form the alloy into ingots and mark it as such, I do not want to come back later & the BHN has "grown" in hardness to 9-10, or whatever it ends up to be, unbeknownst to me. Otherwise, now I would have to go back & retest every ingot before I used it, even though I took the time to put the alloy together the first time. It means , IF the hardness changes, then I need to limit my alloy composition to a certain time range to account for the change.

I think I explained in words what I am thinking & why I asked...
:???:

Hope so anyway.
:)

[OS OK]

JB...when I'm smelting ingots for stowage I keep my batches together...then BHN test one of each batch / stamp that one with ID as to composition and hardness and stow them in rows together. If one changes in the future, it's a simple test to determine that...and, yes...some of my batches have gotten harder when I re-tested months later but at least I know the ingots involved and that they are all changed in the same way.

Ain't it funny how 'OCD' we get over our boolit batches? Kinda like a cook and their recipes!

[Beagle333]

I pulled out a 2 year-old box of .44 boolits yesterday to load up some for the 44-40 and the mic said .431+ and I KNOW they were sized .430 back when they were cast, because they are already lubed!

[Outpost75]

Cellular precipitation occurs in ternary grain structure of unsized bullets, effect also compounded by recrystallization occurring in the plastic deformed region in sized bullets. Use lead-tin alloys without antimony and trace additions of As and Cu as common in scrap alloys to mitigate this effect. Otherwise lube and size immediately before loading and use ammo soon, for match work.

[Shiloh]

I've had .0003-.0004 after a few months. The bigger the original diameter the more you realize. .452 will expand more than .358 and more than .311.
This from adding antimony in the form of linotype.

Waiting to see what happens when I use super-hard alloy and pewter containing 4.2% antimony and 3.6% copper.

Shiloh

[quail4jake]

I think, from all I've read, that age hardening and softening stabilizes at about a month since cast... #1) Does that ring true? #2) Does the same timeline hold true for the expansion phenomena? Thanks, all, for your advice this is really great education and valuable things to know. And yes, OCD! but part of the solution for success.

[243winxb]

Sleeper 1428
as I recall, if the cast was not logged in with date, diameter and as dropped weight, at the time .
There is nothing to compare too. Sorry. :)

[blackthorn]

JB---Thanks for the explanation. Have a great day.