casting temp and alloy vs. dia.?

[451 Pete]

Just thinking this morning. Has anybody ever came up with or seen a formula or rule of thumb as to how much the diameter of a bullet changes by varying the casting temperature or the lead / tin alloy percentage of a bullet? This could be kind of usefull for paper patching or just finding the right combination of temperature and alloy to get as close as possible to the perfect as cast size of any bullet on a first try.

just my thoughts .... Pete

[sqlbullet]

I think the general rule is harder = bigger and hotter = smaller. But I don't know of any formula, and I am not sure of those general rules. I may have them backwards.

After I finished helping my son do his science fair project on lead allow and heat treatment a few years ago, I realized we had missed the boat by not checking diameters of the samples. Someday when I have time I will re-run those experiments.

[451 Pete]

I think the general rule is harder = bigger and hotter = smaller. But I don't know of any formula, and I am not sure of those general rules. I may have them backwards.

After I finished helping my son do his science fair project on lead allow and heat treatment a few years ago, I realized we had missed the boat by not checking diameters of the samples. Someday when I have time I will re-run those experiments.

sqlbullet,
Thanks for the reply. My thoughts are pretty much along the same line. But I just wonder just how much the change is and if it could be calculated. I've never seen anything written on this and it may not exist, but my thinking is that if a fellow could calculate what changes that temperature or alloy would make to the finished bullet it could be a handy thing to know. It could make the difference of weather you could make a bullet mold work or if that mold if off to a new owner.

thanks .... Pete

[williamwaco]

I don't know how much it is but I know it is predictable because every one of the really good custom mold makers insist on knowing what alloy you will be using.

[Defcon-One]

Try a Lyman bullet casting manual. Pretty sure they have a chart on this!

[451 Pete]

Thanks for the replies. I checked again in my books and sure enough they have a chart and a bit of information in the Lyman Cast Bullet Handbook. Lyman molds are sized to cast with the #2 alloy. Pure lead or wheel weights cast a smaller dia. bullet that weigh's more than #2 alloy and Linotype a larger dia. bullet that weighs less. This sounds backwards, but that is what they have got.

thanks again .... Pete

[Sonnypie]

Study metallurgy.

One sure thing is that things expand as they get hotter.
So as the mold temperature goes up, it is reasonable to assume the cavity diameter would show some sort of change.

As for me, I just shove everything through sizing dies to force the issue.
But there are noticeable differences in force between some of the different boolits. Barely noticeable, for the most part, but there none the less.
I have a single cavity that is suppose to throw .311" diameter. I have found some out at .314".
So, to me in my "shade tree ways" it is best to poke them all through a .3105 sizing die for my .3085" slugged rifle bore.
I don't think I want my rifle swagging down .0055 (five and a half thousandths) of over-sized lead.
To me, that would cause some obvious pressure variations.
So I squish um.

You could say I have too much time on my hands.

OH, PS: These are with RotoMetals Lyman #2. Not some shop alloy I conjured up.