Reversing the aging process

[Marlin Junky]

I want to get back into shooting 180-200 grain .30 caliber plain base boolits next week and have noticed that my supply of 311-195's (nominal) have age hardened to approx. BHN 16-16.5. In order to get them back into shape for target shooting, I'm thinking about baking them at 450F for an hour and slowly cooling. My goal is to achieve a hardness in the 13-14 BHN range 4 days after annealing. In other words, anneal tomorrow night, lube and load them into '06 cases on Wednesday night (they're already sized) and shoot 'em Friday morning. These particular boolits are copies of those used to shoot the targets posted on my longer .30 PB (http://castboolits.gunloads.com/showthread.php?184749-Longer-30-cal-plain-base-question&p=2160406&viewfull=1#post2160406) thread and were approx. BHN 14.5 at the time of shooting... which at the time I thought was borderline too hard.

Anyway, I'm trying to get them back to freshly cast status and propel them with a charge of 16 grains of 4759. Targets will be posted on my longer .30 PB (http://castboolits.gunloads.com/showthread.php?184749-Longer-30-cal-plain-base-question&p=2160406&viewfull=1#post2160406) thread on 06-21-13 if it works out.

Actually, if this works out, perhaps I can cast more COWW boolits ahead of time and disregard the aging process by annealing 2-4 days before loading and shooting, respectively.

So, I guess my question is... will baking at 450F for one hour provide enough annealing to remove all age hardening to a COWW alloy?

Thanks,
MJ

[shooter93]

MC....a search may find you the articles written by Charlie Dell. In his book he talks a lot about heat treating and /or tempering bullets afterwards. He did some pretty extensive research and testing for his match guns. You may also know someone handy with his book to lend you.

[Marlin Junky]

MC....a search may find you the articles written by Charlie Dell. In his book he talks a lot about heat treating and /or tempering bullets afterwards. He did some pretty extensive research and testing for his match guns. You may also know someone handy with his book to lend you.

'93,

Thanks for the tip but I've run out of searching patience.

My alloy in question is actually a combination of COWW and softer Pb alloys (stick-on WW metal and/or ballast, spent muzzle loader boolits, etc.) which still contains enough Sb to age harden from about BHN 12 just after casting to 16+ in several months. I don't know exactly what they added to clip-on wheel weight metal during the few years before removing them from the CA market (which is pretty much the time frame in which I collected most of my current alloy); however, my straight wheel weight metal heat treats to BHN 30! I remember back in the good old days, one could melt a boolit cast of WW metal in your moma's oven, but I've actually been able to heat treat my COWW at over 500F in my wife's new-fangled convection oven.

I'm just going to bake 'em at 450F tomorrow, test 'em Wednesday evening and report back. My guess is that they'll be right around BHN 13, two days after removing all the age hardening. At least that's what I'm hoping.

MJ

P.S. Come to actually think about it, I bet "they" stopped using any tin whatsoever in order to reduce cost... I'll bet that would increase the COWW melt temp.

[Marlin Junky]

Hardness testing directly after the 450F anneal revealed a BHN of only 11 which is actually slightly softer than I get during a casting session. Perhaps if I opened the oven door directly after the one hour baking time elapsed, instead of allowing the boolits to cool with the door closed (approx. an additional hour with the heat turned off) the BHN may have been closer to 12. I checked three boolits and got the same results each time.

Unfortunately, I think BHN 11 is too soft for a plain base boolit to be loaded into '06 cases so I'm going to check them again on Wednesday and Friday to see if they've hardened to BHN 12-13. I ran a few of them into my Lyman .311" die that sizes gas checked boolits to .3110-.3115" and the bases were reduced to .3100-.3105".

This little exercise has been very informative. The same alloy (COWW blended with softer Pb alloys) can produce boolits that range in hardness from BHN 11 to 16+ given age hardening and variable cooling conditions. Personally I find this frustrating and it looks like my days of grabbing dusty old boolits off the shelf because they once shot well are gone.

Question: Does tin possess a hardness stabilizing attribute? My current casting alloys are literally dirt cheap.

MJ

[truckjohn]

Nope.. Tin doesn't stabilize hardness.. I believe it's actually kinda the opposite... The more Tin - the more they eventually Soften as they get older and older.... but we are talking like a couple years here....

It's Arsenic and Antimony that primarily cause age hardening..

If you look at the hardness/time curve - it's kinda like a hill that peaks around 1 year, then they some alloys start to soften and others kinda stabilize...

Typically - Lead/Tin binary alloys don't exhibit the same behavior.... which is one of the things that just makes them so wonderful for pistols... The Tin doesn't add much for hardness (for each % tin added,) but it also doesn't really age harden like Arsenic/Antimony does...

Thanks

[badgeredd]

MJ,

One thing I have found is if one ups the soft PB and then adds Sn to the alloy he can get a very stable alloy. I've been using an alloy for softish boolits of 66% purish PB to 33% COWW with about 1 % Sn added. It seems to stay pretty close to 14 BHN over time. Of course MOST of my softer boolits get used up withing a few months. The Sn seems to balance the Sb-Sn ratio.

Edd

[Marlin Junky]

MJ,

One thing I have found is if one ups the soft PB and then adds Sn to the alloy he can get a very stable alloy. I've been using an alloy for softish boolits of 66% purish PB to 33% COWW with about 1 % Sn added. It seems to stay pretty close to 14 BHN over time...
Edd

That's precisely what I'm looking for an... alloy in the 13-14 BHN range that stays there indefinitely. Any softer and it becomes to difficult too handle (e.g., unchecked bases become damaged), any harder and plain base target/varmint boolits don't shoot as well in my '06.

Thanks Edd, I was getting there slowly but you gave me a welcome shove in the right direction. :bigsmyl2:

MJ

[Marlin Junky]

It looks like folks are still reading this, so I'll keep providing info...

I checked the boolits' BHN again last night and they registered BHN 11; i.e., no change from Monday when they were annealed from BHN 16-16.5 to BHN 11. I'll check them again Friday but doubt they will be hardening anytime soon because of the way they were annealed. Again these boolits, under the conditions they were originally cast, registered over BHN 12 a couple days after casting. As expected, casting conditions influence BHN.

So... assuming one can still maintain boolit quality, if one desires a little harder boolit from the same alloy, I bet running up the melt temp a bit and holding down the mold temp a bit will alter the boolit's BHN. In other words, casting a boolit with a little more frost to it should result in a little harder boolit than one with a shine to it (from the same alloy). Perhaps everyone already know this. Perhaps there might even be slight differences in final BHN when casting during the dead of winter vs. the middle of a very hot summer's day... or even if one has a fan blowing on their freshly dropped booits vs. no cooling rate influence at all! We all know how dropping COWW metal into cold water influences final hardness, but I'm pretty sure now that subtle little differences* in casting conditions can alter BHN enough to make a difference.

Anyway, I'll be shooting the above boolits with 16 grains of 4759 next week whether they have hardened to BHN 12-13 or not. I backed off the Lee Collet die to create an inside neck diameter (on my '06 cases) that is more compatible with BHN 11. Last night I seated a couple of these relatively soft boolits (BHN 11) into one of my normally sized Remington '06 cases and I ended up swaging the .120" long bases from .311 to less than .310, which ain't gonna cut the mustard... so to speak. Backing the Collet die off somewhat revealed a reduction in base diameter of only about .0005" with the rest of the boolit shank diameter unchanged... hopefully there will be enough tension to hold the boolits in place in the cartridge case neck after loading. Very soft unchecked boolits are a pain in the butt!

MJ

* Mold material and size too, could influence final BHN since the heat dissipating rate is altered.

[outdoorfan]

It looks like folks are still reading this, so I'll keep providing info...

I checked the boolits' BHN again last night and they registered BHN 11; i.e., no change from Monday when they were annealed from BHN 16-16.5 to BHN 11. I'll check them again Friday but doubt they will be hardening anytime soon because of the way they were annealed. Again these boolits, under the conditions they were originally cast, registered over BHN 12 a couple days after casting. As expected, casting conditions influence BHN.

So... assuming one can still maintain boolit quality, if one desires a little harder boolit from the same alloy, I bet running up the melt temp a bit and holding down the mold temp a bit will alter the boolit's BHN. In other words, casting a boolit with a little more frost to it should result in a little harder boolit than one with a shine to it (from the same alloy). Perhaps everyone already know this. Perhaps there might even be slight differences in final BHN when casting during the dead of winter vs. the middle of a very hot summer's day... or even if one has a fan blowing on their freshly dropped booits vs. no cooling rate influence at all! We all know how dropping COWW metal into cold water influences final hardness, but I'm pretty sure now that subtle little differences* in casting conditions can alter BHN enough to make a difference.

Anyway, I'll be shooting the above boolits with 16 grains of 4759 next week whether they have hardened to BHN 12-13 or not. I backed off the Lee Collet die to create an inside neck diameter (on my '06 cases) that is more compatible with BHN 11. Last night I seated a couple of these relatively soft boolits (BHN 11) into one of my normally sized Remington '06 cases and I ended up swaging the .120" long bases from .311 to less than .310, which ain't gonna cut the mustard... so to speak. Backing the Collet die off somewhat revealed a reduction in base diameter of only about .0005" with the rest of the boolit shank diameter unchanged... hopefully there will be enough tension to hold the boolits in place in the cartridge case neck after loading. Very soft unchecked boolits are a pain in the butt!

MJ

* Mold material and size too, could influence final BHN since the heat dissipating rate is altered.


Yes, I've also noticed how oven annealing them like you did can get straight COWW alloy to 10 bhn and it will stay there, where as air-cooling the boolits in the normal casting process seems to add another couple numbers or so as they slowly age harden. I'm sure the cold winter air will net a harder boolit than warmer summer air for those who cast outdoors.

[Marlin Junky]

Yes, I've also noticed how oven annealing them like you did can get straight COWW alloy to 10 bhn and it will stay there, where as air-cooling the boolits in the normal casting process seems to add another couple numbers or so as they slowly age harden. I'm sure the cold winter air will net a harder boolit than warmer summer air for those who cast outdoors.

Thanks for the input. My alloy wasn't straight COWW. It actually has quite a bit of GOWW (G for glue), some fishing net weights (which could have some Sb), roof flashing, etc, (anyway, a whole bunch of softer stuff).

Have you fiddled around much with different annealing temperatures? For example 400F, 450F... even 500F, perhaps?

It would be nice if we can correlate an annealing temp to a reduction in air cooled, aged hardness.

MJ

[outdoorfan]

Thanks for the input. My alloy wasn't straight COWW. It actually has quite a bit of GOWW (G for glue), some fishing net weights (which could have some Sb), roof flashing, etc, (anyway, a whole bunch of softer stuff).

Have you fiddled around much with different annealing temperatures? For example 400F, 450F... even 500F, perhaps?

It would be nice if we can correlate an annealing temp to a reduction in air cooled, aged hardness.

MJ


I almost exclusively use 50/50 COWW/Soft, and of course the annealing temperatures will be different than with straight COWW's. I did a bunch of this a few years ago with the 50/50 alloy, but I stupidly didn't make it a point to save what I had written down 'cause I can't find it right now.

I want to say that getting the 50/50 to around 16 bhn (from 21 bhn) took about 325-350 degrees or so, but I'm not sure (it was too long ago).

If I remember correctly, pretty much any temperature over 400-425 resulted in a dead soft boolit as far as the alloy could anneal to, so your results at 450 seem to be right on. I would aim for maybe 375 for an hour (letting them cool down slowly with the door closed) to try for 13-14.

Another method which I briefly tried is to boil them in a pan of water. I did this with the 50/50 alloy and they seemed to stop softening once they reached 14ish bhn. I needed them at 12, so I ended up throwing them in the oven to finish the job.

I think a forum member here (Robs) has done quite a bit of testing with straight COWW's and can give some hard numbers on oven temperature to final bhn.

[popper]

Add Sb and Cu to get the hardness you need. It will be stable in two days..

[Marlin Junky]

Thanks for the input, outdoorfan...

50/50 is indeed a versatile boolit alloy; i.e., from BHN 10 to 30 simply with the aid of a kitchen oven.

I don't know where I'm going to get the trace of As if/when I run out of COWW metal though!

MJ

[outdoorfan]

My 50/50 alloy oven-anneals to 8.5-9 and oven-HTs to 21ish. The straight WW's that I've tested would do 10ish on the low end and 30ish on the high end.

[outdoorfan]

Oh, one more thing. I've found that when trying to oven-anneal boolits that there may be only a few degrees to separate one bhn hardness level from the next level. For example (hypothetically), 375 might get you to 14 and 385 will be 16. It can be rather touchy.

[Marlin Junky]

My 50/50 alloy oven-anneals to 8.5-9 and oven-HTs to 21ish. The straight WW's that I've tested would do 10ish on the low end and 30ish on the high end.

You know, the more Pb you add to the alloy, the higher the melt temp. Have you tried 500F+ in the oven for about 90 minutes prior to quenching with your 50/50?

Perhaps you have no need for an alloy harder than 21 though.

MJ

[Marlin Junky]

Oh, one more thing. I've found that when trying to oven-anneal boolits that there may be only a few degrees to separate one bhn hardness level from the next level. For example (hypothetically), 375 might get you to 14 and 385 will be 16. It can be rather touchy.

Are you paying close attention to your warm-up, baking and cool down times in those comparisons? I usually get better consistency during heat treating by baking for 75-90 minutes opposed to shorter intervals, so I assume the same would be true during the annealing process.

MJ

[Baryngyl]

Thanks for the input, outdoorfan...

50/50 is indeed a versatile boolit alloy; i.e., from BHN 10 to 30 simply with the aid of a kitchen oven.

I don't know where I'm going to get the trace of As if/when I run out of COWW metal though!

MJ

I believe you can get the As from shotshell shot.


Michael Grace

[outdoorfan]

You know, the more Pb you add to the alloy, the higher the melt temp. Have you tried 500F+ in the oven for about 90 minutes prior to quenching with your 50/50?

Perhaps you have no need for an alloy harder than 21 though.

MJ

I think the highest I've set the oven to was 490 or so. I get nervous going much higher than that in case they start to slump.

Are you saying that you've gotten 30 bhn out of 50/50?

[outdoorfan]

Are you paying close attention to your warm-up, baking and cool down times in those comparisons? I usually get better consistency during heat treating by baking for 75-90 minutes opposed to shorter intervals, so I assume the same would be true during the annealing process.

MJ


I never baked them that long...probably only 30-45 minutes typically. That's one question I have. I figure the boolits are as baked as they'll ever get by 30 minutes. However, maybe not.

I try to be as consistent as possible in the bake times and when I take them out, which is usually right after the cycle light goes off.

[Marlin Junky]

I think the highest I've set the oven to was 490 or so. I get nervous going much higher than that in case they start to slump.

Are you saying that you've gotten 30 bhn out of 50/50?

It was probably more like 60/40, but yes... and I think it was at the maximum setting on my wife's convection oven, 525F IIRC.

BTW, the boolits in my little annealing project were closer to 12 tonight... I wonder just how accurate the Lee tool is though. I've got the spring well lubed but I can't help wondering if it drags sometimes on the walls of its housing.

MJ

[Marlin Junky]

I believe you can get the As from shotshell shot.


Michael Grace

That's right!

MJ