How does alloy mix affect casting size?

[383]

I'm not sure if I worded title correctly, so here goes. Though being new to casting, I can understand how the actual ratio of alloys can affect the actual weight a bullet is when it drops from the mold due to different densities. However, from reading posts here about different molds, I keep seeing folks mention how this or that mix will cause a bullet to drop at a certain diameter.

Am I reading that correctly? If so, can someone explain how that works?

Thanks!

[shredder]

I think I know the answer, but as new as I am to all this, I won't pretend to be any authority since I lack the first hand knowledge. I will watch the responses with interest and see if I can confirm or deny what I have read.

BTW< Great question!

[44man]

Antimony alloys age expand some. Depends on boolit diameter as to how much with smaller calibers gaining less. Pure lead does not change and makes the smallest. As you change the pure lead to gradually make it harder, the change is very small at each step and will peak at some alloy and going harder has no more affect.
Cold molds make larger boolits then over heated ones. With any alloy, once you reach the frost point or more, the boolits will be smaller. Pure will not frost but the same thing happens and because pure needs more heat, molds made for pure lead are cut larger. A good mold maker will ask you what alloy you use and factory molds are based on what each alloy the factory uses as a standard.
My large bore boolits can age grow .002" but in most cases you are only going to see .0005" to .001".

[383]

Thanks for the explanation. I'm looking at one of the Accurate molds and I will be casting with isotope alloy.

[44man]

Great molds. Just tell them what your alloy is and I am sure they will get it right for you.

[youngda9]

I believe tin reduces serface tension and makes slightly larger bullets IIRC.

[243winxb]

Quote:<Did someone miss seeing the QUOTE? Need new glasses?
The bullet diameters and weights presented in this list
are based on the use of Taracorp’s Lawrence Magnum
bullet alloy (2% tin, 6% antimony, 1/4% arsenic,
91.75% lead).
Bullet diameters and weights will vary considerably
depending on the lead casting alloy used. This variation
can be as much as 1/2% on the diameter, and 8% on
the weight among the most commonly used casting
alloys. For example, a .358-158 grain bullet might
show a diameter variation of .002", and a 13 grain difference
in weight.
Of the most commonly used alloys, wheel weights (.5%
tin, 4% antimony, 95% lead) will produce bullets having
the smallest diameter and heaviest weight, with
such bullets running approximately .3% smaller in
diameter and 3% heavier than bullets cast with
Taracorp's metal. Linotype will produce bullets with the
largest diameter and lightest weights. This alloy will
produce bullets approximately 1/10% larger and 3%
lighter than Taracorp. Other alloys of tin and antimony,
with antimony content above 5%, will produce bullets
with diameters and weights falling between those cast
from wheel weights and linotype.
Alloys containing little or no antimony will cast considerably
smaller than wheel weights and in some cases
will produce bullets too small for adequate sizing.
Within the limitations given above, the weight and
diameter of a cast bullet can be adjusted by varying the
alloy’s antimony content.
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.

[shredder]

"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"


That is something I had not considered. There is much science at work here for something that seems so simple. Great explanation from 243winxb.

[myg30]

Lots of great reading below at the lasc.us click on it and read on. There is sooo much to learn and get confused about. The main thing to remember is that after you cast a boolit and work up a load for it you want to be able to repeat the same process. I try to weigh my lead mix before I melt in the pot. The lead may be slightly different but at least the ratio of pure lead to ww and tin are close.
243 you did a real great job and I hope the op will read on.

Mike

[383]

243winxb,

You've given me a lot to digest!

[runfiverun]

you guy's know that is out of a book right?
I am amazed at the stuff people write down for others to read.

[detox]

Why does pure lead shrink more than linotype when both are cooled?

[44man]

I can't answer if pure shrinks more but an alloy with antimony will grow some when aged.
Another thing to consider is pure needs more heat, about 800*. When the mold gets hot enough, the cavities also get smaller because they are on an edge, not a hole in the center of a block.
This might be the hardest thing to see because a hole will increase in size but half a hole on an edge will shrink.

[Shiloh]

Antimony alloys age expand some. Depends on boolit diameter as to how much with smaller calibers gaining less. Pure lead does not change and makes the smallest.
My large bore boolits can age grow .002" but in most cases you are only going to see .0005" to .001".

+1 on this

[383]

I can't answer if pure shrinks more but an alloy with antimony will grow some when aged.
Another thing to consider is pure needs more heat, about 800*. When the mold gets hot enough, the cavities also get smaller because they are on an edge, not a hole in the center of a block.
This might be the hardest thing to see because a hole will increase in size but half a hole on an edge will shrink.

Hadn't even considered the mold aspect.

[Larry Gibson]

Quote:
The bullet diameters and weights presented in this list
are based on the use of Taracorp’s Lawrence Magnum
bullet alloy (2% tin, 6% antimony, 1/4% arsenic,
91.75% lead).
Bullet diameters and weights will vary considerably
depending on the lead casting alloy used. This variation
can be as much as 1/2% on the diameter, and 8% on
the weight among the most commonly used casting
alloys. For example, a .358-158 grain bullet might
show a diameter variation of .002", and a 13 grain difference
in weight.
Of the most commonly used alloys, wheel weights (.5%
tin, 4% antimony, 95% lead) will produce bullets having
the smallest diameter and heaviest weight, with
such bullets running approximately .3% smaller in
diameter and 3% heavier than bullets cast with
Taracorp's metal. Linotype will produce bullets with the
largest diameter and lightest weights. This alloy will
produce bullets approximately 1/10% larger and 3%
lighter than Taracorp. Other alloys of tin and antimony,
with antimony content above 5%, will produce bullets
with diameters and weights falling between those cast
from wheel weights and linotype.
Alloys containing little or no antimony will cast considerably
smaller than wheel weights and in some cases
will produce bullets too small for adequate sizing.
Within the limitations given above, the weight and
diameter of a cast bullet can be adjusted by varying the
alloy’s antimony content.
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.

More should read and then re-read several times the articles in Lyman's Cast Bullet Handbooks (#3 & #4 specifically) and even the casting articles in Lyman's reloading manuals (#49 being the latest) about alloys and how to cast properly. Might save a lot questions and grumbling about moulds not casting to size.........seems we must constently reinvent the wheel........

Larry Gibson

[383]

I have both on order, and believe me I will dig in when I receive them. I have learned a lot and found it unnecessary to ask many other questions by reading other threads and stickies. I apologize if my asking of this particular question annoyed you.

Best

[243winxb]

you guy's know that is out of a book right?
I am amazed at the stuff people write down for others to read.

The "Bullet Sizes & Weights – How to Vary Them" info is from Saeco & can be found online. http://www.redding-reloading.com/ind...-moulds-charts The photo of BNH is from the instruction sheet that came "FREE" with a Lyman mold, containing full instructions on how to cast bullets.

[Phlier]

Gents, please forgive me bumping this rather old thread, but I learned about this very subject over the past few days the hard way.

I spent many months reading here at castboolits, read the Lyman Cast Bullet Handbook, and From Ingot to Target before I cast my first boolit. Somehow, I either completely forgot about it, or missed the information entirely.

There is some great information in this thread. Learning how not just alloy composition but also alloy and mold temps effect the diameter of a boolit is good stuff.

In my particular instance, I bought a new NOE .358 mold, hoping to size to .357 for use in 9mm. Al at NOE told me it would throw a bigger bullet with my Lyman #2. I was quite surprised to find out how big: .362-.363. Too large to size down to .357. I haven't had a chance to try it with a different alloy yet, but may give it one more try with a warmer mold and alloy to see if I can get it down to .360-.361.

Now please don't think I'm bashing NOE here at all. Al told me it would throw large with my alloy. This is not on him or his mold, it's on me. My NOE mold is top notch quality. The boolits it casts have a maximum of .0005 runout, and often have such low runout that my calipers can't measure it! Besides, this just gives me a reason to buy another NOE mold... I'll use it for Lyman #2, and the one I have now for COWW alloy.

I'd like other new guys to learn from my mistake... Know what your alloy of choice will do to cast boolit diameter prior to pushing the Buy button on a mold.

Also know that mold and alloy temps will change boolit size, too.

Big thanks to everyone who added their knowledge and references in this thread. You guys really helped a fellow caster.

Going to add a few words here to hopefully make this very educational thread easier to search for: bullet alloy diameter size variation

[georgerc]

I must have been casting cold as most of mine are oversized, heavier than advertised too, not to rule out the lee mold isn't perfect but this was the first time, I remember seeing them frost up and reduced heat, maybe a little too much looking back, that and I got some lead slash in between the mold halves, I'll tinker some next time see what happens