Temp question..

[NSP64]

Will the same alloy cast at different temps cast different size boolits?

[geargnasher]

Yes, but mould temperature affects size more than alloy temperature per se.

Gear

[NSP64]

So, if your mold is up to temp casting with alloy at 700* and 800* which boolit will be bigger?

[lwknight]

There may be no true answer to your question.
I don't think it would matter much as long as you do not over heat the mold.
The alloy is cooled solid even as its filling the mold. By the time you get the base filled , the nose is already solid unless your molds are entirely too hot.
In which case you will likely get shrunken band syndrome.

I never cast at over 700 degrees and often 650 is hot enough. Once the molds are hot , I get the best sustained production rate at 650 degrees.

[cbrick]

Will the same alloy cast at different temps cast different size boolits?
Yes, but as was already said, mold temp is more important. The hotter bullet will shrink more upon cooling and give a very slightly smaller bullet. Either way, hotter or cooler it will probably not be enough to matter much or do you much good. It would be measured in the tenths of a thousands.


So, if your mold is up to temp casting with alloy at 700* and 800* which boolit will be bigger?
Next point, if you have any tin in your alloy your pot should never see 800 degrees. The purpose of the tin being there is to reduce the oxidation of Sb/Pb in the stream of alloy into your mold, be it from a bottom pour or ladle. Tin looses it's ability to do this past 750 degrees and past this temp tin itself oxidizes faster.

If your alloy is roughly 100 degrees past it's liquidus temp, let's say that is 700 degrees, that is all the heat your pot/alloy ever needs to be. Think of the logic, 700 degree liquid alloy will very easily keep your mold in it's proper casting range, somewhere around 400-450 and if the casting pace is increased 700 degree alloy can easily and quickly get your mold too hot. A higher pot temp than 700 degrees will not help you cast better, it is only tough on your alloy. It will also slow your casting pace as you continually wait for the sprue and the mold to cool.

Rick

[Bret4207]

I'm sure somewhere in the metallurgical world there's a formula for figuring size variation and shrinkage after casting with a particular alloy and mould. I have no idea where you'd find it. In practical terms a hotter mould and alloy will give you slightly smaller diameter boolit, but IME that difference is in the tens of thousandths and varies with mould type and alloy. And then you have the tendency of some alloys to "grow" a bit as they age...kinda hard to give and definite opinion as to just what will do what in a particular condition.

There! That's a REAL helpful post...

[onesonek]

There may be no true answer to your question.
I don't think it would matter much as long as you do not over heat the mold.
The alloy is cooled solid even as its filling the mold. By the time you get the base filled , the nose is already solid unless your molds are entirely too hot.
In which case you will likely get shrunken band syndrome.

I never cast at over 700 degrees and often 650 is hot enough. Once the molds are hot , I get the best sustained production rate at 650 degrees.

I can attest to your mold temp issue! Advising me to slow down my tempo because of the hot mold and frosting, made all the difference in the world.
Remember that first session pic LWK, the difference in dia. was significant too,,,well at least in my mind. The shiney ones just as fill out was right and mold temp was not too high consistantly measured (.45-70 in this example) .4596" with the alloy I was using. The frosty ones varied from .4583-.4586". To me that has to affect chamber pressures enough to raise cain with accuracy. Not too mention that smallest dia. was under my slug dia by .0002"
The second pour slowing tempo as I said made a big difference in appearance, but more importantly dia consistancy. However, I must have been doing something else inconsistantly, or me running that alloy at 720-740,,,,the alloy didnt like. I know it hasnt been long, but I'm noticing as much at 2 points in hardness,(measure the same spot on different boolits). I am going to run another pot today with the same alloy, and back the pot temp off, to your running temps
I don't know that 2 points in hardness would make a difference, but I would think so from a pressure point veiw. Moreso, I'm just interested in more consistancy,,,,that will come in time I'm sure. Maybe it's just the difference in time, from which I'm dropping from the mold???

[truckmsl]

I run my 30, 35 and .40 cal aluminum 6 cavity moulds at over 800F. I get excellent fill out and weight consistency with very few, if any, rejects. I lay the filled mould on a wet sponge for about three seconds each time before dumping boolits in water. Using a second pot and transferring lead to the first when half empty I can easily cast 750 boolits in an hour. I have never had good luck with cooler temps. I have noticed no detrimental effects to my alloy, even with tin added. No theory - just experience.

[cbrick]

I have never had good luck with cooler temps. I have noticed no detrimental effects to my alloy, even with tin added. No theory - just experience.

Well, it is theory, your theory. Either that or the entire metals industry is wrong.

If your happy with your results you should of course keep doing exactly what you have been doing but because you didn't "notice" simply does not change the metallurgy.

Rick

[sqlbullet]

Not only will the be a little smaller, if water dropped they will be harder (assuming you have an alloy that will quench-harden).

In my testing with 96/3/1 isotope lead, casting at 650° and water dropping averaged 25 BHN. At 700° this jumped to 29, and at 750° this was 32.

[geargnasher]

Not only will the be a little smaller, if water dropped they will be harder (assuming you have an alloy that will quench-harden).

In my testing with 96/3/1 isotope lead, casting at 650° and water dropping averaged 25 BHN. At 700° this jumped to 29, and at 750° this was 32.

Now that's interesting. Never did a test on water-quenched boolit hardness vs. pot temp. I'm assuming they all were checked the same time after casting?

I'm getting about 22 out of water-quenched .45's using Sam's large containers, almost exactly the same as clip-on WW.

Gear

[sqlbullet]

They were all cast the same day and tested the following day. Age-hardening should not have been an issue.

The lead used would have been the equivalent of mixing Sam's large containers 50/50 with is small containers, fluxed with sawdust and used motor oil. I mention that because the used motor oil will introduce a variety of trace metals that may act as further grain refiners/hardening agents.

There is a chart at the bottom of this page (http://fellingfamily.net/isolead) with the complete results. This was for my son's science fair project in 5th grade.

[Centaur 1]

I only have experience using Lee aluminum molds so I don't know to what extent other mold materials are effected. It's been my observation that bullet diameter gets larger as the mold gets hotter. Lead may shrink more when it has to cool from hotter temps, but like others have said it's a very small amount. I believe what's happening is the mold expands as it heats, just like when you put a torch to a rusted nut.

[mooman76]

I agree with Centaur 1 although it may or may not be true in all cases. I was trying to get small boolits out of my Lee Minie moulds in .500 caliber. The miniie as most know here are suppose to slide down the barrel easy but mine were a little tight. I noticed that my first ones were dropping just over .500 and coming out like .501/2. The ones after awhile when the mould got hotter were coming out more like .503/4. This of coarse was with soft lead alloy.

[Fixxah]

I don't know what temp my bullets are poured at but it is just above the point where the spout on my pro-melt freezes up.

[Railbuggy]

My Lyman Cast Bullet Handbook,third edition,1980 says 750F is a normal casting temperature.Just sayin,I don't know.:???:

[geargnasher]

My Lyman Cast Bullet Handbook,third edition,1980 says 750F is a normal casting temperature.Just sayin,I don't know.:???:

If you'd read the whole thing you'd know it also says to start at 100* over liquidus of the particular alloy you're using for starters and only increase if you aren't getting good fillout (I'll add: ...good fillout with an adequately heated mould), which even with pure lead is only 725* or so, MUCH less with most of the ternary alloys we use. My experience concurs, but most people won't know what full liquidus really is by looking so it might be best to shoot for 125* or so over what they think is a completely molten alloy.

Keep in mind that the same book says that zink-contaminated lead alloys are "unrecoverable", only shows load data for Lyman #2 alloy and Linotype, often recommends sizing to groove diameter, and many other small but misleading things that have been thoroughly debunked here.

Gear

[Bret4207]

I can attest to your mold temp issue! Advising me to slow down my tempo because of the hot mold and frosting, made all the difference in the world.
Remember that first session pic LWK, the difference in dia. was significant too,,,well at least in my mind. The shiney ones just as fill out was right and mold temp was not too high consistantly measured (.45-70 in this example) .4596" with the alloy I was using. The frosty ones varied from .4583-.4586". To me that has to affect chamber pressures enough to raise cain with accuracy. Not too mention that smallest dia. was under my slug dia by .0002"
The second pour slowing tempo as I said made a big difference in appearance, but more importantly dia consistancy. However, I must have been doing something else inconsistantly, or me running that alloy at 720-740,,,,the alloy didnt like. I know it hasnt been long, but I'm noticing as much at 2 points in hardness,(measure the same spot on different boolits). I am going to run another pot today with the same alloy, and back the pot temp off, to your running temps
I don't know that 2 points in hardness would make a difference, but I would think so from a pressure point veiw. Moreso, I'm just interested in more consistancy,,,,that will come in time I'm sure. Maybe it's just the difference in time, from which I'm dropping from the mold???

Are you saying your fresh cast boolits are different Bhn compared to the ones cast earlier? That's age hardening if you test both at the same time. Test both at the same time after each was cast and you results may be closer.

[onesonek]

No Bret, the same batch,,,,,, I tested 10 samples at the same time (48 hrs after cast). One of them ran a full 2 points under the rest. The rest were close. One point may not have really raised my attention, but 2 seemed odd to me.

[sqlbullet]

Onesonek points out another issue I noticed while helping my son develop his data.

We were testing statistically significant groups of bullets. I didn't post the standard deviations with the data, and will have to track them down. IIRC the bullets that were air-cooled or water-dropped from the mold had significantly higher deviations than the bullets that subsequently were oven treated.

So, if you really want good consistency in your bullets, you are going to want to heat treat them post casting. Even if you are just wanting air cooled bullets, heat them to 350° for one hour and let them cool in place. This will give you a very uniform BHN.

One other item of note. Even though the samples cast at the higher temp were smaller in diameter (slightly) they were also usually .5-1 grain heavier. They also were capable of a greater hardness when going through oven heat treatment at 450° for an hour followed by a quench. This all indicates the bullets have a greater density when cast at the higher temp.

[cbrick]

the bullets that were air-cooled or water-dropped from the mold had significantly higher deviations than the bullets that subsequently were oven treated.

So, if you really want good consistency in your bullets, you are going to want to heat treat them post casting. Even if you are just wanting air cooled bullets, heat them to 350° for one hour and let them cool in place. This will give you a very uniform BHN.

Exactly! And an excellent point on HT/anneal for consistency when an air cooled BHN is desired. Age hardening will still occur after this anneal just as with any type of cooling your castings.

For those that shoot mostly short range handgun loads this variation of BHN would probably make little to no difference.

However, long range higher velocity handgun and/or rifle loads destined for the best possible accuracy this is not only important but critical to achieve the best possible success.

I did extensive long range revolver testing with BHN and BHN variability explained in much more detail here: Heat treating lead/antimony/arsenic alloys (http://www.lasc.us/HeatTreat.htm). A minor BHN variation of 1 or 2 BHN within the same 5 shot group made little difference, a larger variation in BHN such as 15-20 BHN within the same 5 shot group made a huge difference in accuracy. This difference could not only be seen on the target but also on the chronograph. More BHN variation than about 5 and even hitting the 150 meter target became "ify" much less grouping.

Rick

[Bret4207]

Wow! This is good stuff, very interesting. Keep it coming guys, this is sticky territory.

[Daddyfixit]

Just a comment on temps, I have to run much hotter for the Mihec brass moulds, around 800 deg to get clean sharp fill out. I tried 700 deg but even with added tin I needed to turn up the temp. My RCBS moulds are fine at 700 deg or so.. The Lee moulds don't care what the temp is!

[cbrick]

Just a comment on temps, I have to run much hotter for the Mihec brass moulds, around 800 deg to get clean sharp fill out. I tried 700 deg but even with added tin I needed to turn up the temp.

Hhmmm . . . Your not looking at it from the right angle. 700 degree liquid alloy poured into a brass, or iron, or aluminum mold will get that mold up into a good casting temp and easily keep it there. Conceivably you could get the mold temp all the way up to 700 degrees and the alloy would not freeze for a very long time. It is no problem for 700 degree alloy to keep the mold at a proper casting temp which should be somewhere around 400-450 degrees. Pre-heating the mold simply saves you the time of several extra pours to get the mold temp up but pouring 700 degree alloy into any mold will easily raise the mold temp up to the 400-450 range.

A higher pot temp is plain and simple not needed and is detrimental to the tin first, then the antimony and then the lead. No sense buying tin and putting it in your alloy if it will do you no good and it won't past around 750 degrees so says the metals industry. Leave the pot temp at 700 degrees and simply pour faster. Don't look at your alloy as lead, look at it as heat, your not pouring lead, your pouring heat and the heat is hot enough but the mold your pouring heat into is not yet hot enough so pour the heat a little faster giving the mold less time to cool off between pours. If your pouring two fills a minute then pour three, if that doesn't do it pour 4 a minute.

Take a look at my avatar. That is WW + 2% tin cast at 700 degrees in a Miha 4 cav brass mold, it's the 45 Cal 270 grain SAA PB. The photo below is is my current avatar.

Rick

[mpmarty]

That's funny, today I cast 500 230gr 45acp boolits and tried to keep the melt at 700 degrees. All the boolits turned out fine with nearly no rejects other than the first pour where the bases were rounded. Using a LEE six cavity TC/TL mold. The boolits are well filled out and quite shiny. I did not cool the mold between casts and worked fairly fast. Had to wait to let the pot catch up a few times when I added more ingots. Spout would freeze up at anything below 675 degrees.

[lwknight]

Thats the rub about using a 6 banger with large cavities.
The waiting on the pot almost lets your molds get too cool.
A hot plate is a great help.
You can also preheat your ingots on the hot plate.
Just be sure that you actually put a steel plate between the burner and the ingot.
Also , don't have a fan blowing on the spout. It will freeze it up.

[cbrick]

That's funny, today I cast 500 230gr 45acp boolits and tried to keep the melt at 700 degrees. All the boolits turned out fine with nearly no rejects.

Thanks for that, I have about run out of ways to explain that 700 degree alloy temp is hotter than a 400-450 degree mold temp. That the 700 degree alloy will attempt to make the mold equal it's temp thus raising the mold temp. Lot's of folks simply do not want to believe that. Strange.

Rick

[lwknight]

Thanks for that, I have about run out of ways to explain that 700 degree alloy temp is hotter than a 400-450 degree mold temp.

You and me both.

[onesonek]

The wife came home early my last casting session, and noticed the toaster oven was missing. Then proceeded to ask where it was,,,,,"ahh, umm, ahhhh,,,,it's outside keeping my boolit mold warm, while waiting for rejects and sprues to remelt"
Hope she don't miss that mixing bowl I took for tumble lubbing.

[geargnasher]

Onesonek, you're treading on very thin ice, my friend. Aquaint thyself with the thrift store or Target/Walmart/whatever rather than the couch or the doghouse.

Gear

[geargnasher]

You and me both.

I'm glad you two guys are on the ball with that, I'm just getting tired of trying to explain, in ways that are understood, how ALLOY temperature and MOULD temperature are two different things, and that the ALLOY is best maintained at a temperature based on its individual metallurgical requirements, and the ideal MOULD temperature is maintained by CASTING SPEED, not ALLOY TEMP.

Many, many people cast way too slow, then crank the pot up to 850* with WW alloy to compensate for this, and if it helps the fillout a little bit, they draw the wrong conclusion from what they did, and now they think CRANK THE HEAT on the alloy. What they should be thinking is FOUR POURS A MINUTE, FOUR TO SIX SECOND SPRUE SET.

Gear

PS Hey Bret, how's the "Casting 101" sticky project coming? Think we could just stop at "Fit is king, 100* over liquidus, mould at 400-450* no more than 2% Sn, Felix Lube or White Label, .001" over groove diameter (usually), pull a boolit and measure it, yes you can shoot it without the gas check" ??

[Dannix]

Hum, maybe we could sticky this thread for as a stopgap. Would be a good stopgap too -- great beginner stuff here.

[Bret4207]

I'm glad you two guys are on the ball with that, I'm just getting tired of trying to explain, in ways that are understood, how ALLOY temperature and MOULD temperature are two different things, and that the ALLOY is best maintained at a temperature based on its individual metallurgical requirements, and the ideal MOULD temperature is maintained by CASTING SPEED, not ALLOY TEMP.

Many, many people cast way too slow, then crank the pot up to 850* with WW alloy to compensate for this, and if it helps the fillout a little bit, they draw the wrong conclusion from what they did, and now they think CRANK THE HEAT on the alloy. What they should be thinking is FOUR POURS A MINUTE, FOUR TO SIX SECOND SPRUE SET.

Gear

PS Hey Bret, how's the "Casting 101" sticky project coming? Think we could just stop at "Fit is king, 100* over liquidus, mould at 400-450* no more than 2% Sn, Felix Lube or White Label, .001" over groove diameter (usually), pull a boolit and measure it, yes you can shoot it without the gas check" ??

Well, yeah, we could do that if we wanted it simple and peoples reading compensation was up to par. But you keep forgetting- this is MAGIC! You have to use MAGIC SMOKE or MOULD RELEASE to get the boolits to drop at all and you have to add MAGIC TIN to make your boolits HARD CAST because soft won't shoot (what's this anti-money stuff anyways?) and Lee moulds just don't have a drop of MAGIC in them. And if you have enough MAGIC stuff you can go out and shoot boolits with standard jacketed loads right off the bat. But most guys don't buy enough MAGIC! Besides, it's a 308 and I shoot 308 jacketed bullets so it makes sense I need a .308 sizer. And I don't really want to spend the extra money on gas check for my $4500.00 Richguyspecialtacticalelitewhizbangmagnum. They're expensive.

Yeah. Maybe it would fly if we had more magic words. That's why convincing people 700 degrees is hotter than 400 degrees is so hard and that pot and mould temp are two different things, no magic!

[onesonek]

Onesonek points out another issue I noticed while helping my son develop his data.

We were testing statistically significant groups of bullets. I didn't post the standard deviations with the data, and will have to track them down. IIRC the bullets that were air-cooled or water-dropped from the mold had significantly higher deviations than the bullets that subsequently were oven treated.

So, if you really want good consistency in your bullets, you are going to want to heat treat them post casting. Even if you are just wanting air cooled bullets, heat them to 350° for one hour and let them cool in place. This will give you a very uniform BHN.

One other item of note. Even though the samples cast at the higher temp were smaller in diameter (slightly) they were also usually .5-1 grain heavier. They also were capable of a greater hardness when going through oven heat treatment at 450° for an hour followed by a quench. This all indicates the bullets have a greater density when cast at the higher temp.


After re-reading this thread again,, more and more sinks in.
Shooting no matter what, for me it's always about consistancy. I hadn't given much thought, but heating and slow cool down, but it certainly makes sense. Regardless of alloy, if one doesn't have consistant hardness whether it be heat treated and quenched, wter dropped, or air cooled, I think it woud be difficult to reach the accuracy potential.


Exactly! And an excellent point on HT/anneal for consistency when an air cooled BHN is desired. Age hardening will still occur after this anneal just as with any type of cooling your castings.

For those that shoot mostly short range handgun loads this variation of BHN would probably make little to no difference.

However, long range higher velocity handgun and/or rifle loads destined for the best possible accuracy this is not only important but critical to achieve the best possible success.

I did extensive long range revolver testing with BHN and BHN variability explained in much more detail here: Heat treating lead/antimony/arsenic alloys (http://www.lasc.us/HeatTreat.htm). A minor BHN variation of 1 or 2 BHN within the same 5 shot group made little difference, a larger variation in BHN such as 15-20 BHN within the same 5 shot group made a huge difference in accuracy. This difference could not only be seen on the target but also on the chronograph. More BHN variation than about 5 and even hitting the 150 meter target became "ify" much less grouping.

Rick

Since reading that article sometime back , and now with the above, I think I'm going to get one of those Breville Convection Oven I believe you mentioned.
Upon research, other less costly makes don't have near the positive reviews, and others would be a total waste of money.

Then too, the wife can have her toaster oven back,,,lol

[cbrick]

onesonek, mine is a Cadco Unox (Italian brand) but I can't see what differrence the brand would make as long as it's a decent quality that doesn't conk out AND the interior is large enough to hold the pans you decide to use.

Rick

[onesonek]

Ok Rick,,,not sure where I got the idea on Breville, but I agree, on having decent quality.