Age hardening and the gift of patience

[buck1]

A blanket statement like that is childish.
Rick

I agree, just too many varriables to say.. all ,always,never,etc.
What load,pressure etc...
If a light load will work with a soft boolit fine. As for me , I must agree with rick on this one.......Buck

[geargnasher]

Kind of back on topic:

I use range lead and tin for my .45 acp loads 'cause I want ammo that knocks down bowling pins at 8 yards quickly. I use ww and tin to load my Sharps to shoot groups that are pleasing to me at 100 yards. If I had a longer range I'd be using that.

So, for the topic let's get back to ww in a rifle. I have been casting these and using a technique to harden by freezing. One of the main reasons to use wheel weights is because of the arsenic in the metal which is present to cold harden or "chill" the metal for hardening. It is supposed to nearly double the hardness of wheelweights. Some of this hardening effect is lost over time, but stabilizes at some value higher than "as cast".

Is there anybody here using this method? Is there any validity to this?

Kind of back on topic, but not really.

I haven't done it myself, but someone here (BABore I think) has studied the effects of ambient temperature on the rate of age-hardening and IIRC freezing the boolits slowed down the age-hardening process dramatically, and a mild warming in the oven accelerated the rate to just a few hours.

Here, I found one of the threads...http://castboolits.gunloads.com/show...t=freezer+oven

Gear

[RobS]

Correct on the temps. I will often use an oven to speed up the aging of my boolits. Two to three hours after cast simply put in at 200 degrees for an hour and then leave the boolits in the oven to cool. WW boolits can reach their age hardness in 48 hours with this approach. Two exposures with a minimum of 7-8 hours in between sessions and the aging can be done in 12-24 hours depending on the time between.

Also using a quality oven thermometer helps in keeping oven setting consistent as not every oven is correct with its dials etc. and to hot can actually reverse the process keeping boolits soft.

[myfriendis410]

What I read indicate that the presence of arsenic allows for cold hardening by freezing i.e. "chilled shot". This is supposed to double the hardness of ww. I haven't actually tested the difference, but noted the bullets frozen for 48 hours were much harder to size. I got it from the treatise on bullet alloys from the LASC (great source of information).

[geargnasher]

What I read indicate that the presence of arsenic allows for cold hardening by freezing i.e. "chilled shot". This is supposed to double the hardness of ww. I haven't actually tested the difference, but noted the bullets frozen for 48 hours were much harder to size. I got it from the treatise on bullet alloys from the LASC (great source of information).

Nope. Antimony and trace Arsenic are present in all hardness grades of shot. Chilled shot has the least, and is the cheapest. Magnum shot has the most of both, and is the hardest, and most expensive, commonly having 6% or so antimony content.

All shot is "chilled" as it hits the quenching liquid, "chilled shot" is just a term for low-grade stuff, has nothing to do with freeze-hardening.

Gear

[felix]

Actually, arsenic is used as a lead shot coagulator using its strong surface tension capabilities. Most "impurities", one of which is arsenic, cause a wild freezing point and a long slush stage amongst lead, tin, antimony alloys. ... felix

[cbrick]

What I read indicate that the presence of arsenic allows for cold hardening by freezing i.e. "chilled shot". This is supposed to double the hardness of ww. I haven't actually tested the difference, but noted the bullets frozen for 48 hours were much harder to size. I got it from the treatise on bullet alloys from the LASC (great source of information).

Nothing on the LASC site about "freezing" alloys but yes, great source of information.

Gear and Felix are correct about arsenic in shot, shot won't drop round without it.

Rick

[myfriendis410]

Yeah; I just went back over the LASC website. What is weird is, I'm SURE I read about freezing for 48 hours ww cast bullets as a hardening technique. I must have been hallucinating on vapors off my lead pot or something. Maybe CRS has set in. I remember the article talking about heat treating with a convection oven and found all of that info again.

I suppose I need to revisit all of my after-casting procedures. Damn.

[cbrick]

Yeah; I just went back over the LASC website. What is weird is, I'm SURE I read about freezing for 48 hours ww cast bullets as a hardening technique. I must have been hallucinating on vapors off my lead pot or something. Maybe CRS has set in. I remember the article talking about heat treating with a convection oven and found all of that info again.

Well, you may have read that . . . Someplace.

It wasn't however on the LASC site. I've never posted any such a thing, I've never even heard of doing this.

There are those that believe age softening after heat treating is much more rapid than it is and feel that if they are stored in the freezer after HT age softening will be arrested. The truth is that age softening after HT is a fairly slow process and keeping them in a freezer is hardly worth the effort unless you don't plan on shooting them for 25-30 years or so.

Rick

[myfriendis410]

Well, sorry about the misdirection. That's gonna bug me.......

[BABore]

I currently use 50/50 WW-Pb alloy for the bulk of my shooting needs. Being lower in antimony and arsenic that that of common clip-on WW's, they seem to take a bit longer to stabilize in hardness. When I used straight WW alloy, I did alot of experiments on water dropping, oven heat treating, annealing, and curing time. In most all cases, with both WW's and 50/50 alloys, I have found that measured hardness peaks at 1-4 days. For most low pressure applications (below 25 kpsi), I did see much difference in accuracy whether I shot the boolits on day one or a month later. I have seen some difference in some loads that operate in the 25-40 kpsi range. Not all the time and it depended on the gun. Above 40 kpsi is where I noted the main difference between week old boolits and those aged 1-2 months or more. The accuracy difference wasn't simply blown groups, but those one or two unexplain flyers in each group. When I would notice this going on, I would make myself a note to retry that same load a month or so down the road. In every case, the older boolits shot more consistently. I will still shoot young boolits to get that glimmer, but always wait a bit longer to see what is really capable.

One question/comment I have for Gear and others in regards to age growth. A couple years back I came acrossed a batch of 400 grain 475 cal boolits I casted about 2-3 years prior. I was getting loaded up for a shoot with some fellow members here. These boolits were cast from straight WW's and oven heat treated. One box was checked, sized, and lubed at 0.478. The second box was oven heat treated only. Who knows, maybe I ran out of GC back then. My normal procedure is to OHT, check and size in a nose-first push-through, then lube. Both boxes were OHT'd together and measured 28 bhn after 1 week. Now, 2-3 years later, they still measure 28 bhn. Good as it blew that old wives tale away. When I went to size and GC the second batch, I couldn't get them through my Rockchucker. Upon mic'ing the boolits, I found that they had grown from 0.478+ to 0.483. Just under 0.005" of growth. In a panic I checked the already dressed boolits. They were still at the sized diameter of 0.478. I ended up annealing the big boolits, OHT'd again, and sized right away.

It got me wondering about the sizing of a heat treated boolit just after it was HT'd. I've never found that it degrades hardness if done within 24 hours. I have found, through further experimenting, that sizing after heat treating will arrest any growth in the sized areas only. Just looking for comments on if you've had similar findings.

[cbrick]

Similair experience except it never occured to me to check the diameter.

I was cleaning out the cabinet under my loading bench and discovered a few boxes of RCBS 35 200 gr. FN, properly labeled with alloy, date of HT, sized diameter and BHN. They were 10 years old.

I expected them to be putty after 10 years, they had been oven HT'd to 30 BHN and sized .357" for the throats of my FA revolver, they had been stored at room temp for 10 years. I checked the BHN on several of them and they were still 26 BHN. Sadly I never thought to check for any aging diameter increase. My routine is to cast and then gas check and size within a few days then oven HT. When I am ready to shoot them I then lube them in a die .001" larger than the sizing die.

Your bullets still at 28 BHN after 3 years and mine loosing 4 BHN in 10 years could be accounted for by the 7 year difference or by the percentage of tin. A higher tin percentage will age soften a bit quicker, my standard alloy is clip-on weights plus 2% added bar tin.

Rick

[geargnasher]

BABore, you have much more experience with the long-term studies of this than I do, and this is one of the things I've recently taken great interest in, since boolit growth weeks or months down the road has a really annoying effect on precisely fitted boolits seated in cases with the necks turned to give an exact loaded neck clearance dimension. Growth of even .0005" can take a good thing and make it a dangerous thing in short order if the tolerances are tight enough.

I find it interesting that your boolits stopped growing if they were sized right away, but maintained BHN even after the undized ones grew. I've never had a boolit grow more than about .002", in .45 Caliber, but I don't have many that are more than a year or two old. I did have one batch of 60/40 COWW/SOWW+ 1%Sn cast in 452374HP and sized .453" and lubed from about three years ago that I was going to ship to another member to try out, just for grins I checked them and they were .455". I zipped them throught the push-through again to make them the size I told him they'd be, but a question mark remained in my mind about what old boolits in my stockpile cabinet are doing while I'm asleep. I never did check the bhn of the aged ones, they were about nine a few weeks after casting, and performed very well in the .45 ACP. The only record of that I have is notes on targets.

I've noticed some basics, that arsenic content of an antimonial alloy affects the timeline of aging (duh), but how direct that correlation is between rate of age and rate of growth, I couldn't say. It seems from a few observations that most of the growth with air-cooled alloys happens right along with the hardening, but I have yet to do a really scientific study.

Generally, I work on a project-by-project basis, casting boolits ahead of time and shooting them in a week or a month, rarely stockpiling until I settle on a final load. There are only about three calibers that I care to be this precise with, and the boolits I stockpile for experimenting get sized and lubed just before loading since I'm not doing any super-hard heat treating with them, or the alloys are soft enough heat-treated to not be a problem sizing months after casting/heat-treating.

I'm paying more attention now to growth factors now, so it will be interesting to see more specifically what trends show themselves.

Gear

[btroj]

Babies, do you think the OHT made a difference in the growth over time? In other words, would they get the same size wether heat treated or not?
How does water dropping affect future growth of a bullet? I water drop everything out of convenience and wonder if that is why I haven't had trouble with bullets getting fatter with time.

This sure looks like an area screaming for a good, solid study. Too bad it requires months or even years to get a good handle on things.

Brad

[RobS]

btroj:
Brad,
What do you mean, it's only details and just because we can measure it, it doesn't mean it matters........................................... . I believe that is what you said.



BABore:
Bruce,
I've noted that sizing shortly afterwards also reduces the growth of antimony alloyed boolits as well and if done shortly after casting less than 1 BHN has been tested on the drive bands doing things this way. I don't have any lying around that are 2 and 3 years old. Like Gear mentioned it sounds like you are on top of us all in regards to this topic. I've used my oven at 200 degrees to speed up the aging process and I'm going to do some work on as cast diameter and BHN a few hours after casting and then do some "speed aging" in the oven and record the results just for light of experimenting.

[cbrick]

Well, a month and a half doesn't do it. The only thing I'm currently heat treating is for my long range FA 357 top end loads, this revolver likes 18 BHN. They are cast, sized & gas checked and then into the oven. My Star .357 die sizes my alloy at .3569" to .3572", if enough are measured that is about the spread and the average.

The throats on the FA are .3570" and very uniform, the bullets are a mild snug fit, if they grew much at all they will not chamber.

6 weeks ago I HT'd 500 for the next year or so, when sized (before HT) the diameter miked spot on. I just went and checked 9-10 of them, zero growth, not a tenth. Its only been 6 weeks for this batch but I typically do 400-500 at a time and a year or more later before they are used up and when loaded and fired they chamber perfectly so I can assume that a year+ doesn't grow them.

Rick

[geargnasher]

Interesting. That's one more example of sizing "green" boolits killing the age-growth. I wonder if this is a trend. Never thought of it before.

For the stuff that really matterson exact size, like I said, I size right before loading and shooting just to be sure, so I haven't created much of an opportunity to tell.

Gear

[cbrick]

I have many different containers of various bullets, some cast years ago and never used. They are all un-sized and not heat treated. I usually keep pretty good notes on things like as cast diematers, casting date etc. In the morning I'll see what I have that may be of use to this thread, ie, see if any grew on me.

Rick

[BABore]

Babies, do you think the OHT made a difference in the growth over time? In other words, would they get the same size wether heat treated or not?
How does water dropping affect future growth of a bullet? I water drop everything out of convenience and wonder if that is why I haven't had trouble with bullets getting fatter with time.

This sure looks like an area screaming for a good, solid study. Too bad it requires months or even years to get a good handle on things.

Brad

I have only observed the age growth with heat treated boolits. I haven't looked into any air cooled samples.

As far as water dropped verses oven heat treated boolits, I don't see any difference in hardness values at all. My WW boolits always get to 28-30 bhn with either method and my 50/50 always hits 20-22. I try to maintains a specific casting cadence and mold temperature so the results are the same. I rarely OHT anymore, now that I have it down pat.

As Gear mentioned, in alot of cases age growth is unwanted as the boolit already fits well. But, there are also cases where you may have a bore rider with a smallish nose. A bit of age can do wonders.

I have previously posted that I have experimented and tested the concept of producing a boolit with a hard shell and progressively softer core. With bigger boolit diameters it's fairly easy to do with good temperature control and alloy selection. IMO this is partly the reason that a longer cure time after hardening produces a more accurate boolit. It's easy to hardness test the boolit exterior. I always get max peak hardness withing a few days. When testing core hardness, the only reliable method I found was expansion tests in media. The quenched boolit has its exterior rapidly quenched while it's temperature is above the threshhold where hardneing occurs. It gets hard fast. What about farther into the boolit? There's a depth point where the alloy will harden and then a bit farther in where it won't because convection pulled the heat below the threshhold. I think the farther you get away from the exterior, the slower the hardness is to peak at this depth. That is likely why you have to wait longer for the accuracy and consistency. Increase the antimony and/or temperature before the quench and you deepen the transition point, decrease the wait time, and increase final hardness. Just theory on my part, but I got glimmers of this when I was playing around with HT temperatures and media tests. Myself, I like to cast a good hunting alloy that's hard, tough, and has a soft core for expansion. I purposely operate just above the HT temp threshhold and prefer to wait on my boolits.

[btroj]

I agree on the internal hardness thing with you. I like an allot for hunting that will heat treat to a higher Bhn yet stay malleable enough to upset some. This is mostly for my 45-70.
I don't shoot enough off a bench to be able to say that I have noticed differences in accuracy based upon how long a bullet has been sitting around.
This is an area that I need to look into more. I have a few bullets that fit pretty snug when cast, I wonder how they fit now?

RobS- when I say that it is only detail and that just because we can measure it dent mean it matters I mean just that. I can hardness test a group of bullets and say that some are 15 bhn and others are 19 bhn. This may have no real world affect on anything. If you are a plinker and they both shoot to your needs, did the differing hardness matter? I am only trying to point out that not everything has a practical application in all shooting arenas. If I was shooting for small groups I would weigh my bullets, I don't shoot for group so I don't. To me, it doesn't matter so I don't measure it.

This has been an interesting discussion on age growth. I have never personally seen it but don't doubt at all that it exists. Sadly, I mostly shoot Ruger an Marlin firearms and they aren't too picky about a fat bullet. That may be part of why I haven't seen this, my guns allow even a fatter than normal bullet to chamber.

Brad