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[joeb33050]

MOLD AREA, BULLET WEIGHT AND CASTING SPEED

This article is about maximizing "good bullets per hour" of casting time; why some molds slow us down when casting and suggestions from casters about how to fix the problems that slow us down.
I think that there are only two things we can vary in bullet casting, the temperature of the pot and time. Temperature is easy, but time has several components.
Time the spout is in contact with the sprue plate or is keeping a molten puddle of alloy on the sprue plate.
Time between moving the mold from the spout and opening the sprue plate.
Time between removing the bullet and closing the sprue plate and starting the next pour.
Time has some value to us, even to old retired guys like me. I'd like to cast good bullets faster.
The "fixes", below, are necessary because there's an imbalance between the alloy freezing temperature and the mold dimensions.
If the mold is too small, it has to be cooled down.
If the mold is too big, it has to be heated up.

Reports from well-instrumented bullet casters state that during the casting process, molds cool off more than I'd ever expected, from ~500-550F to ~250-350F between solidification and re-pouring. Molds are excellent heat dispersers. Heat dispersion with molds of a given material, iron or brass or aluminum, in still air, at room temperature is a function of the total heat in the mold and the surface area of the mold.
If the mold is going to cast a great big bullet, the mold needs to be big.
If the mold is going to cast a small bullet, the mold needs to be small.
Optimum mold size, for maximum casting speed, is a function of bullet weight, and maybe dimension ratios; but certainly of bullet weight.

Molds are classified as "hot", "ideal" or "cold" here.
"Hot" molds require cooling off between pours, a slow pace of casting that results in fewer good bullets being cast per hour than with an "ideal" mold. An example is my Ohaus 45-405 single cavity (SC) mold that casts 45 caliber 433 grain bullets, but not many good ones per hour.
"Ideal" molds will cast good bullets as fast as you can go through the casting steps, with no waiting time between pour and open-the-mold. These molds are just right; normal, unhurried and un-slowed cycling through the casting steps gives us good bullets, fast.
"Cold" molds require a lot of mold heat-up time and quick casting. If you stop for a bit you get wrinkled bullets. These molds are too cold. An example is my custom #78-185, a 185 grain 30 caliber SC mold that produces wonderful bullets, slowly.

ALLOY EFFECT
Different alloys of lead (Pb), tin (Sn), and/or antimony (Sb) melt at different temperatures. Most of these alloys go through a slushy stage between completely solid and completely liquid. The metals; lead, tin and antimony do not go through a slushy stage. Some alloys have a sharp solid-liquid temperature, with no slushy stage. These are called "Eutectic" alloys.
Here is a table of temperatures where the metals or alloys are solid, slushy (if they are slushy), and liquid. All temperatures in degrees F

Metal or alloy Solid Slushy Liquid Note
38.1% Pb/61.9% Sn 361.4 Not 361.4 Eutectic, "63/37"
Tin 449 Not 449
Linotype 463 Not 463 Eutectic
91% Pb/2% Sn/7% Sb 463 <<Slushy between>> 525
88.8% Pb/11.2% Sb 484.2 Not 484.2 Eutectic
94%Pb/6%Sb 486 <<Slushy between>> 550
90% Pb/ 10% Sb 486 <<Slushy between>> 500
95% Pb/ 5% Sn 522 <<Slushy between>> 597
97.5% Pb/ 2.5% Sn 608 <<Slushy between>> 617
Lead 621 Not 621
Antimony 1166 Not 1166

Source: The Art Of Bullet Casting, Jerry Gonicsburg On "ALLOYS FOR CAST BULLETS"
Note that the numbers given above may vary slightly by source. For example, CAST BULLETS by E.H. Harrison, page 16, has the eutectic lead/antimony alloy as 87.3% Pb/12.7% Sb rather than the 88.8% Pb/11.2% Sb above.
For a continuous although virtually incomprehensible graph of melting points of lead, tin, antimony alloys, see the Lyman CAST BULLET HANDBOOK, third edition, pg. 47.
The important things about this, to me, are that (1) lead, tin, antimony metals and alloys melt at widely varying temperatures, and (2) the melting temperature generally goes down as tin and/or antimony are added to lead.

"Cold" molds may operate OK when casting in linotype or other tin-and/or- antimony-rich alloys such as linotype; this because these alloys melt and solidify at lower temperatures than alloys with higher lead percentage, such as 25:1. An example is the RCBS 22 caliber 55 grain double cavity mold. Some casters report this mold as very cold, others, casting in linotype, report this mold as ideal.

BULLET SHAPE
Pistol bullet molds do not seem as sensitive to the "hot" characteristic as do longer rifle bullets. My guess is that bullet with shapes approaching spherical transmit less heat to the mold than do longer thinner bullets.

AGGRAVATION TOLERANCE
To some degree the "cold"-"ideal"-"hot" characteristic of a mold is a reflection of the aggravation tolerance of the caster. The more blasé casters are happy with molds that drive the more sensitive caster nuts.

MOLD WEIGHT
Many "cold" molds are relatively heavy. I find it easier, less tiring and faster to cast good bullets with a lighter mold; and I am enormously strong. Lighter is better.

MEASURING-THE "IDEAL" MOLD
I took a sample of molds, mine and molds belonging to others, only iron/steel molds. No Hoch molds because the geometry is so different from that of other Lyman or RCBS or NEI or Ohaus molds.
I did a lot of measuring and calculating and casting, and got comments from fellow casters. At the end, there was a pretty clear relationship between the surface area of the mold, (not including the sprue plate), and the nominal weight of the bullet/s. An EXCEL workbook containing all the data, "Mold areas and bullet weight", is in "ERRATA".
Here's how the measurements and calculation were made:
Measure the length, (parallel to the handles), width, (across the mold halves), and height of the mold; then calculate the surface area in square inches.
Divide the nominal bullet weight, (a double cavity 55 grain bullet mold has a nominal bullet weight of 110 grains), by the mold surface area and get "grains per square inch".
The Ohaus 45-405 mold had the largest number of grains of bullet weight per square inch of mold at 49.7 grains per square inch.
The Ohaus mold is "hot" because it has too much lead going into too small a mold.
The custom #78-185 mold had the smallest number of grains of bullet weight per square inch of mold at 15.6 grains per square inch and is too cold because it has too much surface area for the size of the bullet. This mold is "cold" because it has too little lead going into too big a mold.

Molds with between 20 and 40 grains of nominal bullet weight per square inch of mold surface area were "ideal".

FIXES
The perfect fix would be to have mold manufacturers vary mold dimensions to correspond with nominal bullet weight.

When casting with a given mold and alloy we can, and should, adjust the pot temperature to make casting good bullets as fast as possible. A "cold" mold wants the pot and alloy hotter; a "hot" mold wants the pot and alloy cooler. If the alloy is too cool for the mold/alloy combination the bullets will be wrinkled. If the alloy is too hot for the mold/alloy combination the sprue will take a long time to harden, bases will have those rough looking holes at the sprue and the bullets will tend to be frosted.
Allow enough time for the pot temperature to stabilize, experiment with different thermostat settings, and write down the settings and results. A thermometer is handy during this temperature adjustment.
Remember that at some temperature north of 800 degrees F the alloy and/or its constituents begin to oxidize very quickly.

"HOT" MOLD FIXES
(Water + molten lead = explosion. Be very careful with water anywhere near the lead pot.)
From "The Modern American Rifle" A. C. Gould, copyright 1891: "...Before commencing, place a dish of water near you, and a mallet or stick of wood; the first to plunge the mold into when it is growing too hot,"
Now A. C. is talking about a "hot" mold. And what he's doing is cooling the mold off so he can cast faster, so he can get more bullets per hour.
Dick Howes at the Old Colony Sportsman's Association advocated mold cooling by touching the mold bottom or sprue plate to a wet sponge or folded cloth. He was able to cast a lot of good bullets quickly using this method.
Lately, (2008), Bruce B. on the "Cast Boolits" forum has cast amazing quantities of bullets in short times using his adaptation of these cooling methods.

Cast with more than one mold and allow alternate molds to cool between pours.
Cool the mold in a stream of air from a fan.
Cool the mold on an aluminum plate. I've had good luck cooling the bottom of the mold on a flat aluminum plate, and on the bottom of my aluminum muffin pan/ingot mold.
If the mold has two cavities, pouring into just one cavity will reduce the mold temperature and may actually increase production of good bullets.
It has been suggested that replacing the sprue plate on a "hot" mold with a great big sprue plate will make the mold less "hot".

"COLD" MOLD FIXES
Cast a lot with a new "cold" mold. As the mold surfaces oxidize or blue the heat transfer rate seems to go down and the mold gets less "cold". A lot of use doesn't fix the problem, but does lessen it.
Using a mold-prep in or smoking the mold cavity/ies may make the mold less "cold". Some casters suggest using mold-prep on, or smoking, the outside-the bottom and sides of the mold, to make it less "cold" by slowing down heat transfer.
Heat the mold on an electrical hot plate or with a propane torch; or dip the mold in the pot of alloy. These actions may work best when done with varying frequencies, such as before each pour, every second pour, etc.

[Le Loup Solitaire]

Thank you for a most interesting and informative article. I wish that more of them written at this level were available. It certainly ought to be made a "sticky" or placed with the group of select articles submitted and kept for reference by forum members. In my own experiences with the molds that I use, I have noticed many of those characteristics that you have mentioned and discussed and often wondered why such processes were taking place. I could only surmise that there were definite reasons and relationships that were in a certain order and/or balance. I noted and sorted a few of them in my brief notes, but nothing on a scale such as you have done, principally to keep track of which molds worked better in tandem use than others. I do subscribe to the general idea that each mold has its own properties and casting profile, and observing these special characteristics or needs results in more efficient casting. I observe Guy Loverins advice about watching the quality of the castings and not the clock. So I maintain a moderate pace and keep track of temperatures, pot levels, and many of the factors that you have mentioned. They are most relevant and each has its place in the overall formula for good castings. As I'm sure you know, there are many articles done on investigative work done by many well known writers in the realm of bullet casting and such writings can be found in the Art of Bullet Casting or publications by the NRA. I would suggest to you to have your above article submitted, as well, for publication in forthcoming works related to this field. LLS

[Bent Ramrod]

joeb,

There are also some extraneous factors not necessarily related to heat transfer, volume or surface area that affect casting rate. The cavity design has an effect. A lot of blackpowder designs like Ideal 25720, 319247 and 40392 with many square-bottom grease grooves are sometimes quite reluctant to release the boolit until mould and casting cool enough so that the differential in the coefficient of expansion between lead and iron comes into effect. Or, as Ramrod's Rule puts it: "The sexier the cavity, the harder the casting:mrgreen:." I have a two-cavity 40392 that for some reason has a web of about 1/8" between cavities which has a production rate as low as a one-cavity after all the tapping, shaking, waiting and cursing that needs to be done to get the boolits out of the mould is taken into account. It isn't a matter of burrs or other such problems, just the cumulative effect of a multitude of little grooves. The Loverin designs, if they are long enough, are sometimes troublesome, but generally less so with their rounded groove bottoms. Paul Jones' square grease grooves are few and large enough so they do not grab the boolit like some of the Ideal designs. They seem to roll the boolit loose as the cavities are opened, a nice effect.

Also, the outside design and finish of the mould are important. I don't know what Paul Jones puts on the surfaces of his moulds and sprue plates but they shed lead flakes and splashes amazingly well. Aluminum moulds do the same. The finishes on Ideal/Lyman moulds are somewhat stickier. Having lead stick to sprue holes, mould faces and outsides slows the casting rate down, for me at least. Moulds with a lot of lumpy outside screws or cavities for set screws that collect lead are another production reducer.

But outside of these factors, I would imagine a good modeler/simulator could set up a computer program that would relate the weight of the mould, its thermal conductivity, the weight of the lead and the excess needed for sprues, and predict a production rate of optimum castings at an equilibrium casting temperature as determined by the pot thermostat setting and the ability of the operator to maintain a consistent casting cycle.

[John Boy]

Joe, know you love to dig under the sheets down to the bed frame for good information and your post is a good one.

We also might agree, that every mold is like a woman - different

And a casting procedure that I stick to is ...
http://www.longrangebpcr.com/8Phases.htm ... It has not let me down yet for casting large grain rifle bullets. As for revolver bullets - as long as they look good on the towel ... Cast As I May!

[454PB]

When I first started casting, the few printed references warned of the danger of mould warpage by preheating or cooling with water. As I gained more experience and courage, I began preheating my moulds via several different methods you mentioned, with no warpage or problems of any kind. I then began cooling moulds using a damp towel, and again, no problem. Then I got really brave and began just dunking the mould directly in water. Same thing, it controlled mould temperature well and no damage, even with aluminum moulds. I'm talking about a quick plunge, about 1/3 of the mould submerged, not totally under water. I keep the water well away from the casting pot and on a lower shelf, and I don't empty the mould until all the water has sizzled off.

I've been doing this for many years and many thousands of boolits with zero mould warpage or damage.

[mooman76]

I found that for good production it is good to have things well at hand. An assortment of tools you might need, screwdriver for tightening sprew plate a light plastic mallet for tapping the mould to drop stuborn bullets out and I find a light tap to the mould helps it close completely. Lead ready on hand to keep stocking the pot while working. The key is to get a good working rhythem Wonce you break your stride the mould cools down and you aren't cranking out those consistant bullets you want. Pre heating the mould is essential to getting things going quicker with fewer regects. I think some people waste to much time worrying about those "perfect bullets" Just keep cranking until they start dropping like you want. If you slow down fiddling with things to make everything perfect it just takes all the longer before you see good bullets.
I think that is allot of new casters problems. They are so concerned with cranking out those great bullets right away that they never get up to speed to whaere that will be cranking out the good ones. I was showing a new caster how to cast because he was having trouble and he was amazed at how fast I worked and how quickly I was cranking out good bullets. I'm not trying to brag, I just been doing it for so many years that it comes easy now. I watched him work and couldn't believe how slow he was, he just hadn't done it enough to develop the speed needed to keep the mould hot and thus he couldn't get to the point of dropping good bullets. Just keep working. If it takes 50 or 100 to get there it just does and you shouldn't worry about it just keep moving, it isn't like you are waisting lead. It just goes back in the pot.
By the way I seen this caster latter on and he says he's doing allot better at it now.

[copdills]

Thanks alot of good information from all of you

[Bass Ackward]

It's amazing how many people have trouble with heat. When I started casting, I was told heat rises. The hottest part of the blocks will be the top. The only reason that you need excess heat of your melt is to form the nose. So .... make the top, the bottom.

I cast with two molds. When the sprue solidifies I cut it and then set the mold upside down while I grab the next mold. I let it rest like that on wood to keep it nice and WARM while I mold with the other. That gets the heat up in the blocks where it is needed. It also gets it away from where it is causing problems.

What this in turn does is it allows me to lower the temperature of my melt even more which also lowers problems. I don't have to mold frosty to get correct slugs. IF you still have a problem with heat, use a fan to increase cooling. But I don't have problems and the beauty to this technique is that you don't have to have a perfect rhythm to maintain it.

The disadvantage to the water or air cooling techniques is that it requires a temperature balance where you then need a higher melt temp to effect fill on the next go round. So you end up fighting to achieve a balance for time or casting rate and diameter and weight suffers accordingly. I find that it requires a perfect rhythm or zone for me to do well and something always happens to throw that off.

[runfiverun]

i mold much like bass does, trying to maintain mold temp.
and lowering my melt temp as i go.
i also just add sprues back as i go on a constant basis to maintain a heat level.
instead of fiddling with the knobs.
a bit of a balancing act. but you don't get bored. and the pot don't go empty.

[montana_charlie]

I am enormously strong.
A swage designed to be squeezed by hand is probably your fastest method of making bullets.
CM

[44man]

This is going way past enjoyment! :mrgreen: I put the mold in my mold furnace, turn on the pot and when all is hot, boolits come out perfect from number one to number 300 or more. A reject is my fault. I have a ton of molds of all kinds along with all I have made. They all work the same without thought. The only thing I change is the pot temp for a different alloy.
To look for nothing but speed and how many you can cast in an hour doesn't appeal to me. Like I said 1000 times, 100 perfect boolits is better then 1000 if you have to toss a bunch back in the pot. There is no excuse for a rejected boolit.
Relax and enjoy the fact that every boolit does not need to go on a scale or even be looked at. Just lube, load and shoot.
All of you know what kind of groups I get! :drinks:
Bass said it like it is but he will sure have something to say about my hat before this is over! :mrgreen:

[Bass Ackward]

Relax and enjoy the fact that every boolit does not need to go on a scale or even be looked at. Just lube, load and shoot.


That is the point isn't it. Speed is just not a casting factor. It's a total sum game.

Any heat problems I experience are generally due to two reasons. The first is casting before the mold is up to temp. The second factor to weight or dimensional problems attributed to heat issues is poor venting. The better a mold is vented, away from the cavities, the less likely heat will be to be a problem. LBT makes a center line in his blocks between cavities to prevent this and his molds can be run hotter (faster) than most others without losing weight or causing dimensional issues.

[joeb33050]

Thank you for a most interesting and informative article. I wish that more of them written at this level were available. It certainly ought to be made a "sticky" or placed with the group of select articles submitted and kept for reference by forum members. In my own experiences with the molds that I use, I have noticed many of those characteristics that you have mentioned and discussed and often wondered why such processes were taking place. I could only surmise that there were definite reasons and relationships that were in a certain order and/or balance. I noted and sorted a few of them in my brief notes, but nothing on a scale such as you have done, principally to keep track of which molds worked better in tandem use than others. I do subscribe to the general idea that each mold has its own properties and casting profile, and observing these special characteristics or needs results in more efficient casting. I observe Guy Loverins advice about watching the quality of the castings and not the clock. So I maintain a moderate pace and keep track of temperatures, pot levels, and many of the factors that you have mentioned. They are most relevant and each has its place in the overall formula for good castings. As I'm sure you know, there are many articles done on investigative work done by many well known writers in the realm of bullet casting and such writings can be found in the Art of Bullet Casting or publications by the NRA. I would suggest to you to have your above article submitted, as well, for publication in forthcoming works related to this field. LLS

I come here for comment on articles as they are about ready to go in the book. What book?
The Second Edition of the book "CAST BULLETS FOR BEGINNER AND EXPERT" is complete.
This has gone from under 100 to 496 pages produced by well over 140 contributors, and is a non-profit enterprise.

A WORD copy with all EXCEL workbooks and ERRATA is available at no charge on http://sports.groups.yahoo.com/group/CB-BOOK/, in FILES. FREE!!!!!

Also available at LASC.US
Thanks;
joe b.

[joeb33050]

A swage designed to be squeezed by hand is probably your fastest method of making bullets.
CM

Correct, I use the one-hand hand swage, no press. The thumb-plunger method. I do get fatigued a bit swaging .62 caliber 635 grain linotype bullets, after the first 500 or so in a batch.
Thanks;
joe b.

[454PB]

Maybe we confuse "speed" with "productivity". The first printed materials I read some 38 years ago said to warm the mould by casting, and to burn off the protective oil on the mould the same way. How many casters here do that? If I can increase productivity by preheating the mould, or use water to reduce it's temperature, why wouldn't I?

I usually run two moulds at a time, but sometimes I'm doing a relatively small batch, and maybe even using a single cavity or hollowpoint mould. Controlling mould temperature with a propane torch and water is a very effective method.

[flinchnjerk]

joe b
Yeah, I use the thumb-plunger swager too. And if I don't need over 4000 fps, I save on primers and powder by simply throwing the bullet. Underhand.

[montana_charlie]

I can't work a swage by hand, but I am also enormously strong...until after my Saturday night bath.
CM

[joeb33050]

I've added some of the comments, please give me permission to use your writing. I have, of course, made no mistakes-but sometimes I forget things.
Thanks;
joe b.



MOLD AREA, BULLET WEIGHT AND CASTING SPEED

This article is about maximizing "good bullets per hour" of casting time; why some molds slow us down when casting and suggestions from casters about how to fix the problems that slow us down.
I think that there are only two things we can vary in bullet casting, the temperature of the pot and time. Temperature is easy, but time has several components.
Time the spout is in contact with the sprue plate or is keeping a molten puddle of alloy on the sprue plate.
Time between moving the mold from the spout and opening the sprue plate.
Time between removing the bullet and closing the sprue plate and starting the next pour.
Time has some value to us, even to old retired guys like me. I'd like to cast good bullets faster.
The "fixes", below, are necessary because there's an imbalance between the alloy freezing temperature and the mold dimensions.
If the mold is too small, it has to be cooled down.
If the mold is too big, it has to be heated up.

Reports from well-instrumented bullet casters state that during the casting process, molds cool off more than I'd ever expected, from ~500-550F to ~250-350F between solidification and re-pouring. Molds are excellent heat dispersers. Heat dispersion with molds of a given material, iron or brass or aluminum, in still air, at room temperature is a function of the total heat in the mold and the surface area of the mold.
If the mold is going to cast a great big bullet, the mold needs to be big.
If the mold is going to cast a small bullet, the mold needs to be small.
Optimum mold size, for maximum casting speed, is a function of bullet weight, and maybe dimension ratios; but certainly of bullet weight.

Molds are classified as "hot", "ideal" or "cold" here.
"Hot" molds require cooling off between pours, a slow pace of casting that results in fewer good bullets being cast per hour than with an "ideal" mold. An example is my Ohaus 45-405 single cavity (SC) mold that casts 45 caliber 433 grain bullets, but not many good ones per hour.
"Ideal" molds will cast good bullets as fast as you can go through the casting steps, with no waiting time between pour and open-the-mold. These molds are just right; normal, unhurried and un-slowed cycling through the casting steps gives us good bullets, fast.
"Cold" molds require a lot of mold heat-up time and quick casting. If you stop for a bit you get wrinkled bullets. These molds are too cold. An example is my custom #78-185, a 185 grain 30 caliber SC mold that produces wonderful bullets, slowly.

ALLOY EFFECT
Different alloys of lead (Pb), tin (Sn), and/or antimony (Sb) melt at different temperatures. Most of these alloys go through a slushy stage between completely solid and completely liquid. The metals; lead, tin and antimony do not go through a slushy stage. Some alloys have a sharp solid-liquid temperature, with no slushy stage. These are called "Eutectic" alloys.
Here is a table of temperatures where the metals or alloys are solid, slushy (if they are slushy), and liquid. All temperatures in degrees F

Metal or alloy Solid Slushy Liquid Note
38.1% Pb/61.9% Sn 361.4 Not 361.4 Eutectic, "63/37"
Tin 449 Not 449
Linotype 463 Not 463 Eutectic
91% Pb/2% Sn/7% Sb 463 <<Slushy between>> 525
88.8% Pb/11.2% Sb 484.2 Not 484.2 Eutectic
94%Pb/6%Sb 486 <<Slushy between>> 550
90% Pb/ 10% Sb 486 <<Slushy between>> 500
95% Pb/ 5% Sn 522 <<Slushy between>> 597
97.5% Pb/ 2.5% Sn 608 <<Slushy between>> 617
Lead 621 Not 621
Antimony 1166 Not 1166

Source: The Art Of Bullet Casting, Jerry Gonicsburg On "ALLOYS FOR CAST BULLETS"
Note that the numbers given above may vary slightly by source. For example, CAST BULLETS by E.H. Harrison, page 16, has the eutectic lead/antimony alloy as 87.3% Pb/12.7% Sb rather than the 88.8% Pb/11.2% Sb above.
For a continuous although virtually incomprehensible graph of melting points of lead, tin, antimony alloys, see the Lyman CAST BULLET HANDBOOK, third edition, pg. 47.
The important things about this, to me, are that (1) lead, tin, antimony metals and alloys melt at widely varying temperatures, and (2) the melting temperature generally goes down as tin and/or antimony are added to lead.

"Cold" molds may operate OK when casting in linotype or other tin-and/or- antimony-rich alloys such as linotype; this because these alloys melt and solidify at lower temperatures than alloys with higher lead percentage, such as 25:1. An example is the RCBS 22 caliber 55 grain double cavity mold. Some casters report this mold as very cold, others, casting in linotype, report this mold as ideal.

BULLET SHAPE
Pistol bullet molds do not seem as sensitive to the "hot" characteristic as do longer rifle bullets. My guess is that bullet with shapes approaching spherical transmit less heat to the mold than do longer thinner bullets.

AGGRAVATION TOLERANCE
To some degree the "cold"-"ideal"-"hot" characteristic of a mold is a reflection of the aggravation tolerance of the caster. The more blasé casters are happy with molds that drive the more sensitive caster nuts.
From Bent Ramrod on the "Cast Boolits" site
There are also some extraneous factors not necessarily related to heat transfer, volume or surface area that affect the casting rate. The cavity design has an effect. A lot of black powder designs like Ideal 25720, 319247 and 40392 with many square-bottom grease grooves are sometimes quite reluctant to release the boolit until mould and casting cool enough so that the differential in the coefficient of expansion between lead and iron comes into effect. Or, as Ramrod's Rule puts it: "The sexier the cavity, the harder the casting ." I have a two-cavity 40392 that for some reason has a web of about 1/8" between cavities which has a production rate as low as a one-cavity after all the tapping, shaking, waiting and cursing that needs to be done to get the boolits out of the mould is taken into account. It isn't a matter of burrs or other such problems, just the cumulative effect of a multitude of little grooves. The Loverin designs, if they are long enough, are sometimes troublesome, but generally less so with their rounded groove bottoms. Paul Jones' square grease grooves are few and large enough so they do not grab the boolit like some of the Ideal designs. They seem to roll the boolit loose as the cavities are opened, a nice effect.
Also, the outside design and finish of the mould are important. I don't know what Paul Jones puts on the surfaces of his moulds and sprue plates but they shed lead flakes and splashes amazingly well. Aluminum moulds do the same. The finishes on Ideal/Lyman moulds are somewhat stickier. Having lead stick to sprue holes, mould faces and outsides slows the casting rate down, for me at least. Moulds with a lot of lumpy outside screws or cavities for setscrews that collect lead are another production reducer.

MOLD WEIGHT
Many "cold" molds are relatively heavy. I find it easier, less tiring and faster to cast good bullets with a lighter mold; and I am enormously strong. Lighter is better.

MEASURING-THE "IDEAL" MOLD
I took a sample of molds, mine and molds belonging to others, only iron/steel molds. No Hoch molds because the geometry is so different from that of other Lyman or RCBS or NEI or Ohaus molds.
I did a lot of measuring and calculating and casting, and got comments from fellow casters. At the end, there was a pretty clear relationship between the surface area of the mold, (not including the sprue plate), and the nominal weight of the bullet/s. An EXCEL workbook containing all the data, "Mold areas and bullet weight", is in "ERRATA".
Here's how the measurements and calculation were made:
Measure the length, (parallel to the handles), width, (across the mold halves), and height of the mold; then calculate the surface area in square inches.
Divide the nominal bullet weight, (a double cavity 55 grain bullet mold has a nominal bullet weight of 110 grains), by the mold surface area and get "grains per square inch".
The Ohaus 45-405 mold had the largest number of grains of bullet weight per square inch of mold at 49.7 grains per square inch.
The Ohaus mold is "hot" because it has too much lead going into too small a mold.
The custom #78-185 mold had the smallest number of grains of bullet weight per square inch of mold at 15.6 grains per square inch and is too cold because it has too much surface area for the size of the bullet. This mold is "cold" because it has too little lead going into too big a mold.

Molds with between 20 and 40 grains of nominal bullet weight per square inch of mold surface area were "ideal".

FIXES
Mooman76 and Bass Ackward on the "Cast Boolits" site/forum reminded me about heating up the mold and pot of alloy before beginning to cast.
I put the mold on the edge of the Lee 20 pound pot to heat up. I have found that the alloy is ready to cast-is up to temperature-in 30-45 minutes. But I have also found that waiting an hour and a half for the pot and mold to heat up before casting gives me fewer rejects at the beginning. I weigh almost every rifle bullet I cast. The early bullets, from a slightly too-cold mold, look shiny. These are too light, lighter than the bullets cast later in a hotter mold. Without putting the mold in the alloy or heating it with a propane torch or hot plate, I ALWAYS have some shiny early-bird reject bullets. Giving the mold enough time to heat up thoroughly minimizes the number of these rejects. Start earlier!

The perfect fix would be to have mold manufacturers vary mold dimensions to correspond with nominal bullet weight.

When casting with a given mold and alloy we can, and should, adjust the pot temperature to make casting good bullets as fast as possible. A "cold" mold wants the pot and alloy hotter; a "hot" mold wants the pot and alloy cooler. If the alloy is too cool for the mold/alloy combination the bullets will be wrinkled. If the alloy is too hot for the mold/alloy combination the sprue will take a long time to harden, bases will have those rough looking holes at the sprue and the bullets will tend to be frosted.
Allow enough time for the pot temperature to stabilize, experiment with different thermostat settings, and write down the settings and results. A thermometer is handy during this temperature adjustment.
Remember that at some temperature north of 800 degrees F the alloy and/or its constituents begin to oxidize very quickly.

"HOT" MOLD FIXES
(Water + molten lead = explosion. Be very careful with water anywhere near the lead pot.)
From "The Modern American Rifle" A. C. Gould, copyright 1891: "...Before commencing, place a dish of water near you, and a mallet or stick of wood; the first to plunge the mold into when it is growing too hot,"
Now A. C. is talking about a "hot" mold. And what he's doing is cooling the mold off so he can cast faster, so he can get more bullets per hour.
Dick Howes at the Old Colony Sportsman's Association advocated mold cooling by touching the mold bottom or sprue plate to a wet sponge or folded cloth. He was able to cast a lot of good bullets quickly using this method.
Lately, (2008), Bruce B. on the "Cast Boolits" forum has cast amazing quantities of bullets in short times using his adaptation of these cooling methods.

454PB on the "Cast Boolits" site writes:
When I first started casting, the few printed references warned of the danger of mould warpage by preheating or cooling with water. As I gained more experience and courage, I began preheating my moulds via several different methods you mentioned, with no warpage or problems of any kind. I then began cooling moulds using a damp towel, and again, no problem. Then I got really brave and began just dunking the mould directly in water. Same thing, it controlled mould temperature well and no damage, even with aluminum moulds. I'm talking about a quick plunge, about 1/3 of the mould submerged, not totally under water. I keep the water well away from the casting pot and on a lower shelf, and I don't empty the mould until all the water has sizzled off.
I've been doing this for many years and many thousands of boolits with zero mould warpage or damage.

Cast with more than one mold and allow alternate molds to cool between pours.
Cool the mold in a stream of air from a fan.
Cool the mold on an aluminum plate. I've had good luck cooling the bottom of the mold on a flat aluminum plate, and on the bottom of my aluminum muffin pan/ingot mold.
If the mold has two cavities, pouring into just one cavity will reduce the mold temperature and may actually increase production of good bullets.
It has been suggested that replacing the sprue plate on a "hot" mold with a great big sprue plate will make the mold less "hot".

"COLD" MOLD FIXES
Cast a lot with a new "cold" mold. As the mold surfaces oxidize or blue the heat transfer rate seems to go down and the mold gets less "cold". A lot of use doesn't fix the problem, but does lessen it.
Using a mold-prep in or smoking the mold cavity/ies may make the mold less "cold". Some casters suggest using mold-prep on, or smoking, the outside-the bottom and sides of the mold, to make it less "cold" by slowing down heat transfer.
Heat the mold on an electrical hot plate or with a propane torch; or dip the mold in the pot of alloy. These actions may work best when done with varying frequencies, such as before each pour, every second pour, etc.

[454PB]

Joe, you have my permission to use anything I post here.