Oven hardening problem

[Forgetful]

I baked two batches this week, trying to get the baking right so 100% of the boolits I harden are still useable. Here's my problem.. I planned to bake at 480F for 3 hours and then dunk in cold water. I took a cookie tin and drilled out the bottom (for the tray) and made a handle for it, so I could lift and dunk with a pole without them toppling. I had GC'd and sized them first before baking. I'm thinking I need to size first and then harden and then GC them because of the way the bases are bulging out of the GC. The gap between the GC and the bottom-most driving band swells outward nonuniformly.

First bake was 2 hours at 480F, then dunked in cold water. Second bake was 1.5 hours at 480F, then dunked in lukewarm water. Using Hornady copper GC's.

It looks like the weight of the boolit is crushing the bottom of the boolit above the GC, but I don't notice it until I carefully dunk the tin. I briefly inspected them before dunking, and they appeared exactly the same as when I first put them in the oven.

Can someone explain what I'm doing wrong or how to do this right? Should I use a lower temperature? I have a digital oven so I know I'm nailing the temperature.

[jmort]

Too hot too long.

[jmort]

Check this out

http://www.lasc.us/HeatTreat.htm

[CHeatermk3]

+1
Most ovens are thermostat controlled so the way it works is that the heating element is either on or off. The result is your temp setting is a target that is consantly getting bracketed; too hot then the temp falls to the point that the thermo. turns the element back on, for the start of another swing up past the "set point".

a friend of mine put a couple of hundred boolits into his oven to heat treat and had a puddle of alloy as a result.

[Jack Stanley]

When I used to heat treat bullets I used a thermometer to set the oven and get it set just below what my alloy would slump at . Once the oven was set bullets went into carriers that would not allow bullets to tip over like you are using , and would allow water to enter easy when the water time came . Bullet soaked in the heat for only one hour then into very cold water .

I think my target temperature was four hundred and sixty degrees though .

Jack

[Forgetful]

I guess I'll try 460F for an hour, see if that solves the problem. So, there's no problem with GCing after sizing and heat treating?

The ones that became imperfect after this treatment are around 75% of all the boolits, so 2/3rds of those, I could pop off their GC and the rest are still on too tight but I'll recover them after melting them back in the pot... Since these GC's are sized now, I'll experiment with using them as driving bands by placing one in the mold before pouring, after drilling them out accurately. Or could they be re-used on my next batch as GC's?

[Gtek]

Are you annealing checks?

[5Shot]

I size before heat treating, then after to lube and/or apply the GC. More time, but I don't heat treat a ton of bullets. If you do it withing a few hours of the water bath, they will still be soft enough to get through the sizer, and will still harden more with time. Not sure how much softer the driving bands will be than if you did it before, but I have done it and didn't notice any issues.

I use 450 with my oven thermometer - probably not the most accurate tool, and get a final BHN of about 22 with WW + 2%.

[dondiego]

[QUOTE=So, there's no problem with GCing after sizing and heat treating?[/QUOTE]

Wouldn't you want to install the GC's during the sizing operation?

[5Shot]

I do it after all the time. It also prevents water from getting in between the bullet and GC. If you run them into the same size die or a second die that has been honed out a tad, you can seat them without any resizing of the bands at all.

[Forgetful]

That's good news, that others are also separating the steps before putting on their GC. I'm not annealing the GC, and I have no idea what the oven treatment is doing to the copper to make them loose after they're dunked, or outright popping off on their own. I'd love to GC and size in one go but the heat treatment is necessary, and I don't want to heat treat before sizing because "worked lead" softens and I want the driving bands harder than the core, not the other way around. Also the force necessary to size a hardened slug is excessive, since the mold is dropping them at .511 they'll go smooth but aren't so easy if they age-harden, and become quite difficult after hardening. I sized the ones with melted bases and some of them gave me a near-perfect thick bottom driving band. I don't dare shoot them, since they're radially uneven.

I tried sizing them again to reseat the GCs and some held firm and some are still loose. Not happy! I might scrap this whole batch and pour another 200, seating the GC towards the end. I just wasn't sure if there would be a problem snapping the GC onto a hardened slug. Sizing them once should give .510 but it would be more like .5102 or something, and sizing a 2nd time would be closer to .5100... ideally I only want them sized once but I keep facing this catch-22 situation where I do a step more than once which partially undoes a previous step, such as sizing after hardening.

Ok, so new process:

1) drop cast boolit
2) size (using dry lube)
3) heat treat
4) GC & size 2nd time (dry lube)
5) lube (45/45/10)
6) load

[dubber123]

Ovens are all over the place. I spent a decent amount to get a "good" brand convection oven for heat treating, only to find almost 50 degree temp swings during a heat cycle. By placing a tin blocker at different levels and playing with settings, I can keep it within 10 degrees or so. I also limit my heat to 450 degrees to help prevent any slumping. You can get a quite hard boolit, well into the 20's on the Bhn scale with simple WW's at this temp. Don't feel bad, I ruined a few batches figuring it out. Any slump at all, and that boolit is junk to me.

[5Shot]

I just picked up a desk top Lab Oven off of Craigslist...it is really slow to heat and seems to hold a steady temp. I am going to put together a PID for it so that I can really dial in the temp. The PID should hold it +/- 1* with no overshoot (once it learns the oven). I should be able to vary the hardness by using different temps, and it will be repeatable every time.

[243winxb]

http://www.lymanproducts.com/lyman/faqs/ From Lyman " Q: Is there anything I can do to make the bullets harder?
A: Cast bullets can be heat treated to increase their hardness providing your alloy has some antimony present. To heat treat your bullets: Cast your bullets in the normal manner, saving several scrap bullets. Size your bullets but do not lubricate them. Place several scrap bullets on a pan in your oven at 450 degrees and increase the temperature until the bullets start to melt or slump. Be sure to use an accurate oven thermometer and a pan that will not be used again for food. Once the bullets start to melt or slump, back off the temperature about 5 to 10 degrees and slide in your first batch of good bullets. Leave these in the oven for a half hour. Remove the bullets from the oven and plunge them into cool water. Allow them to cool thoroughly. When you are ready to lubricate, install a sizing die .001" larger than the one used to initially size them. This will prevent the sides of the bullets from work-softening from contact with the sizing die. Next apply gas checks if required and lubricate. These are now ready for loading. "

[btroj]

Go a full hour in the oven, it DOES matter. I know because I did 30 min and a full hour and the differences are there.

[cbrick]

Lyman does it again . . .

Forgetful, the bullet base swelling as you call it is slumping and normally the first place it shows up. You can size and check in one operation, then heat treat, after dry lube with a die .001" larger than the die they were sized with. Keep at heat for no less than one hour.

Never trust the dial on your oven, there are as many variations of temp with them as there are ovens. They may be fine for cookies but not for bullets.

The article that jmortimer linked is a good one (I know, I wrote it :mrgreen:) and far more accurate than the Lyman one. The article explains the whole process including oven temps.

Rick

[leadman]

Just a note to casters that use aluminum gas checks and heat treat their boolits. Be sure to install the gas checks before heat treating as it is possible that the gcs will extrude up the side of the boolit when sized.
I had this happen when I heat treated some linotype 22 cal. Bator boolits for testing the Hi-Tek coating at 3,600 fps plus. They were 35bhn before coating and doing a modified baking of the coating they retained 32 BHN.

[Forgetful]

Perfect, this means my oven is giving me a swinging range from 470-490 or 475-485 when I target 480F. If I just back it off 5-10 degrees I can still get the hardness I'm expecting from 480F.

[243winxb]

Different alloy = Different oven temperature, when boolits start to melt or slump.

[cbrick]

Different alloy = Different oven temperature, when boolits start to melt or slump.

True, the higher the Sn percentage the lower the slump/melt temp.

Rick

[dubber123]

Perfect, this means my oven is giving me a swinging range from 470-490 or 475-485 when I target 480F. If I just back it off 5-10 degrees I can still get the hardness I'm expecting from 480F.

Seriously, if you are using any variation of a "toaster oven", even a good one, fool around with moving the trays/racks around with a good thermometer on them. I had wide swings with my oven like yours, but found a placement of the crumb tray that came with it, and placement of the racks that eliminated almost all of it during heat cycles. Took me a good hour to figure it out.

[Forgetful]

Seriously, if you are using any variation of a "toaster oven", even a good one, fool around with moving the trays/racks around with a good thermometer on them. I had wide swings with my oven like yours, but found a placement of the crumb tray that came with it, and placement of the racks that eliminated almost all of it during heat cycles. Took me a good hour to figure it out.

It's an Easy Bake Oven, temp settings are pretty solid.

[leftiye]

It's simple, if your boolits slump lower the temp. Lower it 50 degrees, and test it in the oven for an hour. If it slumps, lower it again and test again. You want the highest temp that doesn't slump - that's what gives you the most hardening. This means that you also need to test in the oven a new alloy that you haven't previously hardened, and keep raising the temp until the boolits slump, then lower about 50 degrees to find the right temp to cook your specific alloy. The difference from a boolit that slumps quite a lot (anything hotter will outright melt the boolit.) and one that doesn't slump at all is about 50 degrees.

[popper]

As Leftiye says. Your alloy solidus temp will vary depending on the number of constituents in it. As is interesting, as you want a small % for HTing but a large % will really mess up the alloy. Lay long, skinny rifle boolits on the side to find slump temp, the nose will bend.

[pls1911]

Pardon my giggles, but we've all suffered similar events...Mine were layed on the side and looked like elogated pyramids. Rolled across the table top they would stall and slide on the flat side. No laugh is as good as when we laugh at ourselves.

I quickly learned that quenching in cold water, 450 degrees for an hour was sufficient heat and duration to put nominal alloys similar to basic ww into the high 20s bhn, and allows plenty of flex in heat variation to prevent slumping. As stated above, buy an oven thermometer at wally world and adjust your oven's temp accordingly...my oven gets set on about 445, then fluctuates between 440 and 460 in the course of an hour.
The baskets described in the RCBS cast bullet book are constructed from hardware cloth, wire woven to 1/4" squares, with 3/4' sides, with bail handles of coat hanger wire from each corner gathered in the middle. Four 8x8 baskets fit on a cookie sheet in the oven and can be dunked on top of each other in a 5 gallon bucket of cold water.
Use a pair of welding gloves for easy handling.
I heat treat "as cast" bullets, then sort them by weight +/- .01 grain lots, consolidate to aggregate +/- .5 grain lots to maximize yield, then check and lube though over size dies. from a single seeion I will normally see a normal bell curve distibution, and get three lots of usable quantities at +/- .5 grain....outlying weights go back into the melt bucket.
For example, most of my 30 cal bullets drop .310 or .311, so after heat treat, I lube and check through a .312 die . which won't "size" at all.
A final finish is completed with a JPW/LLA wash.
After 30 years of casting I've never had a leaded barrel or a lost critter using bullets produced by this technique, and have not had any slumped slugs in recent times.

And yes, it's the regular kitchen oven, middle rack

[243winxb]

Easy Bake Oven- Boolits should not be close to the heating element on small ovens. If there are 2 shelf levels, but a metal tray between element and boolits. The amount of time to bake starts when the oven reaches operating temperature. I did 1 hr. when i tested the method. Went back to air cooled with the correct alloy, works for me.

[Ricochet]

I've had success using the 450 degree setting on the kitchen stove, without checking a thermometer. But I haven't done much oven quenching because it's so much easier to drop 'em in water while casting. Get the mould up to temperature, casting good looking boolits dropped in a pot on the bench so they can go back in the pot, then start water dropping them. When you get in a rhythm with casting, cutting the sprues and dropping them as soon as they're solid, they'll be plenty uniform.

[DonH]

While not the only source of info on the subject of heat-treating by any means, Veral Smith's book "Jacketed Bullet Performance with Cast Bullets" is well worth having.

[Pinsnscrews]

If you are using an Electric Home Oven, put a wedge in the door to keep it cracked a hair. Usually the thickness of an average wooden spoon works very well. The loss of heat through the crack causes the element to stay mostly lit, which cuts the temperature swing down by half approximately.

[cbrick]

It's simple, if your boolits slump lower the temp. Lower it 50 degrees, and test it in the oven for an hour. If it slumps, lower it again and test again. You want the highest temp that doesn't slump - that's what gives you the most hardening. This means that you also need to test in the oven a new alloy that you haven't previously hardened, and keep raising the temp until the boolits slump, then lower about 50 degrees to find the right temp to cook your specific alloy. The difference from a boolit that slumps quite a lot (anything hotter will outright melt the boolit.) and one that doesn't slump at all is about 50 degrees.

Correct except I don't agree with the 50 degree adjustment in one swing. Stand bullets on their base at the highest temp you believe they won't slump. If they will slump at that temp they will in 15-20 minutes. If they don't slump at that temp raise the temp 10-15 degrees and use new scrap bullets for another 20 minutes & do this until they do slump. At that point back off the temp 10-15 degrees and HT your bullets. This is how you achieve max BHN with your alloy. With WW alloy this can get you to 30 BHN, the question is why would you need them this hard? I tested bullets hardened that much and it can be and is detrimental to accuracy.

Rick

[leftiye]

I had this problem the first time I heat treated. I got slumping at the recommended heat - I guess both my oven was off and the lead alloy varied. I had to lower the temp 25 degrees twice to 425 before slumping was stopped. 475 is a temp you hear a lot where HT is concerned. I do believe the temperature swings in most ovens are about 25 degrees also.

Not to say that I disagree with you. I debated putting in the 50 degree reduction with myself when typing. I just didn't think the slush stage was that narrow (25 degrees). That is why I counseled 50 degrees. It is a large amount, but it for sure will get you to solid territory. Like you said it is hard enough to shoot well.

[cbrick]

I should have added that an oven thermometer is needed (I use two) and you need to keep an eye on it because oven temps to swing quite a bit. For a while I used an RV propane oven and it was terrible and I had to sit and watch it, when the temp started to swing up I had to crack open the door till it stopped going up. That was a PITA.

Rick

[Forgetful]

Dropped my oven temp to "475" and only letting it bake for 1.0-1.2 hours. No more droop. I could probably bring it back up to 480, since I'm not going to bake for 3 hours anymore..

So I've got them sized, hardened, moly impact plated (awesome polished finish!) and I am finally ready to lube and load! Brass has been patiently sitting prepped for too long. The cookie tin I'm using as a tray worked even better for the .30 than the .510's, I was able to fit about 300 in it and it didn't buckle when it heated up this time. I pack them together now, the boolits hold eachother up. I had enough of the wobble-domino effect. They come out perfect.

I can't allow myself to harden them at -50 from 480 (430F) because of how drastic an effect it has on final hardness, according to the table over at http://www.lasc.us/heattreat.htm But I will try 485F next if these aren't hard enough.

[cbrick]

Don't forget when using that chart that Sn percentages matter, the higher the percentage of Sn the lower the slump temp exactly the same as in solder.

What are you shooting that you feel you need them so hard?

Rick

[Forgetful]

Don't forget when using that chart that Sn percentages matter, the higher the percentage of Sn the lower the slump temp exactly the same as in solder.

What are you shooting that you feel you need them so hard?

Rick

My Sn content is very low. I assume there was 0% in my base metal (probably close to 0.5% Sn) but I removed any zinc and a little of that tin by using CuSO4. Also assumed WW were 2% Sb. My alloy I've calculated to be about 96% Pb with 3.00% Sb and 1.00% Sn. There are trace metals of Copper, Bismuth, Arsenic, and Silver. I'll send a sample for xray testing to know exact quantities. Trying to keep the Sn really low and the Sb low and get max hardness from heat treating, where 3% Sb is purportedly a minimal amount for good heat treatment. If I want/need them harder, I can increase the Sb to 3.50% or 4.00% and keep following the same heat treatment. I'm trying to keep the brittleness (from Sb) down and maximize hardness for the alloy, since I have a uniform alloy finally. You can get huge swings in BHN with a temp change of 10 degrees so I'm limiting hardness by controlling the alloy content. I can use the temperature variation to fine-tune the hardness I want, instead. Does that make sense? May seem complicated because I'm modifying multiple variables instead of just one but I'm isolating maximum hardness so it might seem backwards.

I'll be pushing 220gr 30cal in an 06. 2250fps to 2500fps. Using the data I collect from testing and experimenting, I'll apply what I've learned to the 50BMG since it's just a scaled-up 06 and nearly everything should be identical. After I've figured out these two calibers, I'll move on to other rifles. The 06 seemed like a natural way to start.

[cbrick]

The 06 results will be interesting. I don't know that any those doing the high velocity testing have used bullets that hard.

2% to 3% Sb will heat treat but have a longer age time to reach final BHN than will an alloy with 5%+ Sb.

Rick

[BAGTIC]

Are you preheating the oven before inserting the bullets? If not you will probably be overheating the bullets because they can be exposed to a lot of direct radiant heat especially with electric ovens with exposed coils before the oven temperature stabilizes. I preheat my oven and place a heat shield (Foil, cookie sheet, etc.) between the elements and the bullets themselves. An hour at 400F has always been sufficient for wheel weight alloy.

[Forgetful]

Are you preheating the oven before inserting the bullets? If not you will probably be overheating the bullets because they can be exposed to a lot of direct radiant heat especially with electric ovens with exposed coils before the oven temperature stabilizes. I preheat my oven and place a heat shield (Foil, cookie sheet, etc.) between the elements and the bullets themselves. An hour at 400F has always been sufficient for wheel weight alloy.

I'm pretty sure the Easy Bake doesn't need preheating. It's just two 100W lightbulbs. But it has a digital readout, see? It's the ultimate edition.
http://www.hasbro.com/commonspot_sites/localize_promos/410_246-_BSA2_full.png