Relationship of casting temperature to boolit size?

[Rickk]

Can someone tell me briefly what the relationship is (if any) between casting temperature and final boolit size? Will boolits cast at, say, 650 degrees end up and different size than if the lead is 750 or 800?

[runfiverun]

a hotter mold/alloy will make larger boolits.
thats why consistency is preached so much when trying to make your very best.
a colder to hotter mold will also have larger weight variances.

[Edubya]

"The size and weight of bullets of a given alloy will also vary according to casting temperature. Higher temperatures will result in greater shrinkage as the bullet cools, thereby producing a slightly smaller and lighter bullet than one cast of the same alloy at a lower temperature"
http://www.redding-reloading.com/pages/bulletweights.html
There are many other things that will determine the weight, size and hardness on the site listed too.
Good luck,
EW

[303Guy]

Higher temperatures will result in greater shrinkage as the bullet cools, ...I have problem with that statement. Does it refer to alloy temperature or mold tempterature? It sounds like alloy temperature. Thing is, whatever the casting temperature is (or was) the alloy will be at one specific temperature when 'freezes' - its freezing point.

If the mold is at or near the freezing point then the alloy will freeze with the mold at a maximum size while if the mold is considerably cooler, the alloy will freeze quickly with the mold at a smaller size but the way the alloy freezes will likely be different. But the amount the boolit contracts after freezing is going to be the same. Is it the chrystal growth that affects the final boolit size - which will be affected by the rate of freezing of the alloy? Someone must have tried higher and lower temperatures and measured the difference. And measured difference in hardness.

I make a mold that freezes from the base up (nose pour) and the difference is visible with the slower cooling nose section being softer and slightly frosted while the faster cooling base section is not frosted. (This produces a 'controlled expansion' boolit).

[stephen perry]

Lets see the bullets. Lead heats up and cools at the same density. Heat does not add a chemical change to lead. Iron and lead are compatible and differences in heat retention are similar. If this wasn't so you would have to wait for the iron or aluminum mold to show a measureable difference in measurement to be able to release the bullet. Which is saying the bullet would have reduce to in size to release which it will not. Maybe right maybe not so right.
Done.

Stephen Perry
Angeles BR

[Rickk]

Using a Lee 255 grain swc mold 45 caliber I ran an experiment last night. Half the bullets I water dropped, the other half were air cooled. (one drop in the water, the next on the cloth) The water dropped seemed to be larger than the air cooled. Not much difference in size from the first-cast bullets to the last ones.
Does this make sense?

[mooman76]

It's been a few years but I was making Mini's for my BP rifle. The mould size was .500 and the gun is a 50 cal. The Mini as most know is designed to slide down the barrel will little to no resistance. This was not happening as the Mini's were comming out .502-3. I did notice the first few bullets would come out slightly smaller. Small enough they would slide down the barrel. So I'm thinking as you get the mould hotter it expands enough to make larger bullets even though it makes since that hotter lead would shrink more due to temp differance. I'm thinking though that different alloys will give you different results.

[runfiverun]

it does make sense if you are waterdropping you have a consistent rythmn going.
the alloy and mold are holding a consistent temp and you are cooling the boolits in a consistent time frame.
whereas air cooling depends on air flow and position in the pile for their cooling rate.
things equal out over time with these,and your size can change in a few days.
i aircool a 45 boolit and size in the same day they pour at 454 i size at 452 for a final size of 453.
cool huh.
alloy has an effect on final size also.
i use an aluminum mold for my 30-30 with waterdropped ww's and tin and the same mold with 4/6 mix and hotter temps for my 7.7 jap and 303 brit [these are air cooled] but the sizes are 3105 ww's and 313 for the 4/6 alloy and temp range.

[243winxb]

"The size and weight of bullets of a given alloy will also vary according to casting temperature. Higher temperatures will result in greater shrinkage as the bullet cools, thereby producing a slightly smaller and lighter bullet than one cast of the same alloy at a lower temperature"
http://www.redding-reloading.com/pages/bulletweights.html
There are many other things that will determine the weight, size and hardness on the site listed too.
Good luck,
EW Great Link Edubya. The shrinkage takes place in the mould as the alloy goes from liquid to a solid. This is how i understand it. Could the info/link be wrong? [smilie=b: Just have to do your own testing to know for sure. [smilie=l:

[243winxb]

Do you find Frosted bullets are smaller in diameter than Non-frosted bullet, same alloy/pot/batch? Opps, more testing.[smilie=l:

[stephen perry]

Before I had a alloy thermometer I would notice with my Lee pot that I would get shiny and frosted bullets from the same alloy same day. What I surrnised is that when I heard the pot buzzing the temp was increasing. Apparently I was just below the frosted stage most of the time and when the thermostat kicked in the temp increase put me into frosty. I will go measure a few in 1/10's and see if I notice a difference in diameter, get back on this.

I noticed this shiny/frosty in 2 particular bullets- 311291 and 311284.

Stephen Perry
Angeles BR :brokenima

[1Shirt]

Might be a good sticky~
1Shirt!:coffeecom

[montana_charlie]

The shrinkage takes place in the mould as the alloy goes from liquid to a solid. This is how i understand it. Could the info/link be wrong? [smilie=b: Just have to do your own testing to know for sure.
Will this 'test' work for you?
Casting smooth-sided paper patch bullets.
Pour the cavity full and wait five seconds for the sprue to freeze.
Do your 'thing' (whatever it is that you use to maintain a rhythm) then cut the sprue and invert the mould...without opening the handles.

As the 'package' cools, the (smooth) bullet will start to slide out.
It starts slowly, and finishes at a fairly good speed.

If you let the cooling happen before inverting the mould, the bullet falls out as soon as you turn it over.

To me, this means the bullet is shrinking as it cools, and will release quickly if it has cooled enough when the mould is inverted.

The first time it happened, it took me by surprise. I had cut the sprue, but had paused to wipe some lead from the side of the (new) mould. When the bullet fell out and thunked on the bench (missing the towel pad) I thought the sprue plate had fallen off of the mould.

CM

[randyrat]

OK i'm confused now.....If i have a 480 mold it throws a 400 grain bullet and i want it fatter, what should i do.................Run a hard alloy hot as hell, cold, or run a soft alloy Hot, cold?............. Use an Alloy HOT,COLD......... Use a Mold HOT, COLD? Or buy another mold.

I always thought i should run a hard alloy hot to get a fatter bullet?

[armyrat1970]

Do you find Frosted bullets are smaller in diameter than Non-frosted bullet, same alloy/pot/batch? Opps, more testing.[smilie=l:

Last weekend I cast some 8mm with my Lee C324-175-R mold using hardball alloy bought from Midway. When the mold was very hot some dropped completly frosted. When it cooled a little they came out nice and shiney. I measured 7 of each and basically they all dropped right at .327. These were all air cooled. I would say at least with this alloy it doesn't make a difference. Will try some with WWS and water drop after the Monday night game and if I get any frosted, will make sure my mold is plenty hot enough to do so, will check the difference on them and get back.

[jdgabbard]

Well, in my experience, if I run the alloy at a lower temp I get smaller boolits. If I run it higher I get normal boolits. If I run the mold cooler I get smaller boolits, if I run it hotter I get BIGGER boolits.

Just about every metal I know of expands when it cools and gets smaller when its hot. However in my experience lead does the opposite. I think the temp of the mold has the largest influence on what the boolits drop at. Hotter = bigger, cooler = smaller.

Just my $0.02

[c3d4b2]

Here is a pretty good link the talks about casting shrinkage.

http://en.wikipedia.org/wiki/Casting_(metalworking)

[lwknight]

OK i'm confused now.....If i have a 480 mold it throws a 400 grain bullet and i want it fatter, what should i do.................Run a hard alloy hot as hell, cold, or run a soft alloy Hot, cold?............. Use an Alloy HOT,COLD......... Use a Mold HOT, COLD? Or buy another mold.

I always thought i should run a hard alloy hot to get a fatter bullet?

OK, I have struggled with this myself recently with a mold dropping slightly small boolits. Antimony does not shrink significantly when cast at lead melting temperatures. According to Lyman the more tha antimony the more they can actually grow as the crystals line up or whatever they do.
I upped my antimony content to 6-7 percent and keep the tin up to 3 percent to get a slightly larger boolit. 1 to 1 1/2 Thousanths in .430

I don't really need hars boolits so I just air drop.

I could not cause any discernable differences with cast or mold temp other than a cold mold casting smaller than a good and warm mold. It does matter the hardness but, thats not the topic.

[montana_charlie]

Well, in my experience, if I run the alloy at a lower temp I get...
If I run the mold cooler I get...

I think the temp of the mold has the largest influence on what the boolits drop at. Hotter = bigger, cooler = smaller.
You are a caster who realizes that alloy temp and mould temp are separate factors, each having it's own effect on results.

The 'knob' determines alloy temp, but rhythm controls mould temp.

You may be correct on the bigger/smaller part, but I have (also) come to believe that it's mould temperature that creates/prevents frost.

CM

[jbc]

Do you find Frosted bullets are smaller in diameter than Non-frosted bullet, same alloy/pot/batch? Opps, more testing.[smilie=l:

yes my frosty boolits are actually .002 to .003 smaller than my non frosted boolits with straight wheelweight alloy in at least 4 of my molds that i tested (posted this in another thread and got some less than friendly feedback but i have proven it to myself so that's all i'm worried about) - now when i add 4%tin i cant seem to get a frosty boolit(i think the tin is keeping the antimony from showing the crystalization).

The most pronounced example of this is my 2 cavity rcbs 32-170-fn - if i cast it hot and frosty it feeds just fine in my 94 but if i cast it cooler(no frost) it won't feed because the noses are .003 bigger

[Rickk]

The last batch of 255 grain Lee .452 boollits ended up as follows:
No discernible difference between frosted and shiny air cooled.
Water dropped were MUCH LARGER. I am not real good with measuring, but all of the aircooled boolits went through my Lee .451 sizer with ease. Seemed to just take off the out-of-round. All of the water cooled ones were very hard going through the die. Perhaps the water cooled ones were harder and therefore more difficult to size? (Tried it as soon as some were cool enough to handle) They did seem to measure about .001 larger as near as I could determine. Alloy was plane WW, unknown composition. Go figure!

[leftiye]

The primary issue is the temperature of the mold (not the alloy). Molds expand as they get hotter - this is to mean the cavities.

Bad news is that if the mold is hot enough th keep the metal from cooling fast enough, then instead of the boolit drawing metal from the sprue puddle - the boolit shrinks instead. This reads EXTRA shrinkeage. Biggest boolits from a given mold happen at hot but not extermely hot mold temperatures. This on my molds is in the 325 degree range when measured with an IR thermometer on the top outside while closed.

To keep boolits from frosting at the too high temperatures, you have to run the melt cooler. So to avoid over hot molds run the melt at 650 -750 degrees and keep the mold just below heavy frosting. Control mold temperature with an adjustable mold heater.

[Cadillo]

"The size and weight of bullets of a given alloy will also vary according to casting temperature. Higher temperatures will result in greater shrinkage as the bullet cools, thereby producing a slightly smaller and lighter bullet than one cast of the same alloy at a lower temperature"
http://www.redding-reloading.com/pages/bulletweights.html
There are many other things that will determine the weight, size and hardness on the site listed too.
Good luck,
EW

This has been my experience during my limited casting career. When I let my melt temp get up to or over 700 F, I get frosting and smaller OD bullets.

[Paulinski]

What is the best way to keep at constant temp on a 20lb Lee pot for ladle casting?

[lwknight]

What is the best way to keep at constant temp on a 20lb Lee pot for ladle casting?

I found several threads on PID temperature controllers here.
I bought one for $44.00 and a $11.95 T-couple. Easy to wire up and it works great.

[armyrat1970]

Just about every metal I know of expands when it cools and gets smaller when its hot.

Just my $0.02

Wouldn't that be just the opposite? In my experience working in the oilfield as a weldor and fitter I find steel or iron expands when heated and contracts when cooled. Same as a mold will expand when very hot and give a larger boolit. It works this way when trying to straighten out beams that have warped or bent from the heat of welding. If the beam has sagged you heat a spot ontop of it and as it cools it contracts and pulls the ends of the beam up. It will sag more when heating because that spot expands, but will draw up when cooling. Because the metal is contracting. If the ends of the beam rise after welding, you heat a spot on the bottom. After cooling the ends will draw down. Same with a nut on a bolt that is hard or has been rusted and you can't get it off. You heat the nut and it expands and is easier to remove. I have done this many times through the years. Water, many liquids, expand when frozen or heated. But not steel or iron or any other metal that I know of. Even liquid mercury expands when heated and contracts when cooled.

[XWrench3]

i would think that as the mold gets hotter, the boolit size would increase, at least somewhat. a mold that is 300 degrees, should be smaller than a mold that is 500 degrees. what i do not know, is what the lead itself will do as it cools down to room temp. in part of my puny little brain, it makes sence that if a boolit solidifies at a larger diameter, it should stay proportionaly larger than a boolit that solidifies at a cooler temp. terrific, ANOTHER experiment to run! LOL!

[theperfessor]

As long as a metal does not undergo a phase change (liquid-to-solid, or from one solid crystal structure to a different solid crystal structure), then all metals I am aware of contract when cooled and expand when heated.

Iron for example undergoes a size change at 1333F when it changes from a Body Centered Cubic structure called ferrite(T<1333F) to a Face Centered Cubic structure called austenite (T>1333F). But without a phase change taking place, I can find no reason for a bullet to shrink to a smaller size when cast hot than when cast at a colder temperature.

A while back I did a limited, semi-scientific test of mold cavity sizes versus mold temperature that examined the old wive's tale that holes get smaller when the metal around them heats up - they don't. This test did not examine the size of the bullets cast from a mold at different temperatures, as was explicitly stated in the thread.

At the present time I do not have the time to examine this issue as it would require several different alloys and require casting enough samples to be statistically significant.

I have plans to make two multi-cavity molds that will cast smooth, cylindrical slugs ranging in size from .250" to .500". One mold will be aluminum, the other using Dura Bar 65-45-12. I want to check shrinkage of different alloys to determine what size a mold should cut to at room (machining) temperature to cast a slug of a certain size using a specific alloy.

When these molds are ready I will cast slugs at a different mold and alloy temperatures and address this issue with FACTS.

[mpmarty]

Thank you Perfessor. Facts are much more interesting than conjecture. I for one appreciate your dedication to finding out what's really happening inside our toys.

[theperfessor]

For the last few years I've been working on a long term project to develop the knowledge and technology to be able to make my own bullet molds, and perhaps at some point offer a few for sale.

I've built all the proper tooling to lathe bore five cavity molds. I'm learning the best way to make cutting tools. The next step is to determine material characteristics and dimensional standards.

I plan to make three five cavity molds from different materials (2024 and 7075 aluminum and Dura Bar 65-54-12 malleable iron) to determine the proper cavity diameter of the mold when used at the proper temperature needed to cast well-filled out slugs from a specific alloy so they will drop at a specified size.

I know from reading the posts here that the major point of dissatisfaction many experienced caster's have is molds that drop bullets the wrong size.

I plan to drill and ream five holes of different diameters - .250", .312", .375", .437 ", and .500" - so that it will cover the range of sizes typically used in cartridge handguns and rifles. The hole sizes and the bullets will be measured at room temperature.

I originally just wanted to compare a hole diameter of X size to a bullet of Y size when cast out of Z alloy when casting at the lowest alloy temperature needed to get complete fillout. I will broaden the test to cover two or more mold/alloy temperatures.

I'm thinking about drilling a couple holes in the mold for a temperature probe so that I can determine the mold temperature and to compare it to the surface temperature I get with an IR sensor.

I'm very busy during the regular school year so I usually work on things such as this during the summer. I acquired all the materials but did not get to work on my mold project this last summer due to some health issues. I'm doing the thinking-through part now and plan to start the physical stuff next May.

Any suggestions welcomed.

[leftiye]

Geez, I musta been speaking Swahili.

[theperfessor]

leftiye -

No, you weren't speaking Swahili. Your post makes a lot of sense in that you have made an observation of a phenomenon backed by measurements and have described a mechanism to explain why it occurs.

As my posts explain, long before I chimed in on this thread I was planning on doing a specific test to develop a knowledge base that would correlate bullet sizes to mold cavities size using several bullet alloys and mold materials. To do this at two or more alloy/mold temperatures would involve an additional amount of work but might provide additional useful information. After all, not all casters cast at the same rate or use the same temperature alloy and some bullet shapes and alloys require different temperatures to cast well.

If/when I get this test done I will publish the raw data and make it available to all to draw their own conclusions from.

I don't doubt your observations, or similar observations made by other people. I just want enough hard, firm, statistically significant data gathered under controlled conditions to be able to make good bullet molds.

[leftiye]

That wasn't aimed at you. I just wondered if I farted or something and no one listened.

[303Guy]

Swahili? leftiye, where are you from?

Lead has a higher expansion coefficient than steel (or iron). Then, when the alloy 'frosts' it is undergowing some crystaline changes so ... ? Hotter alloy, cooler mold, cooler alloy, hotter mold? I await with interest the outcome of some testing.

[243winxb]

The shrinkage takes place in the mould as the alloy goes from liquid to a solid.
When tin is added to lead-antimony alloys, linear shrinkage is reduced. http://www.springerlink.com/content/m55026kr15575q49/ . After the bullet becomes a hot solid, it will contract as it goes to room temperature. [smilie=l: