Dumb ?? about as-cast weight

[singleshotbuff]

Gentlemen,

This is a Noob question as I know I have read it before, but here goes. What causes my boolits to cast heavier than the advertised weight of a mold? Harder or softer alloy??

Example, I am using a new Lee 452-255-RF and my alloy is 50/50 wheelweights and range lead. I drop the boolits right from the mold into a bucket of cold water and they are hard as h3ll (as best as I can tell). This is my standard metal for all pistol loads and I have never had any leading issues and the boolits can not be scratched with a thumbnail (which I know is a meaningless test), so I assume it is fairly hard.

They weigh right at 260grs. I seem to recall a harder alloy would be lighter in a given mold than a softer alloy. Am I remembering wrong?? FWIW this alloy also weighs 163grs from a Lyman 358156 mold, although I am unaware of the predicted weight of this mold.

Not that I am complaining about the weight as they are beautiful looking boolits and should do well in my 45 Colt Ruger Blackhawk, just curious.

Thanks

SSB

[John Boy]

Tip: The size and weight of bullets of a given alloy will vary according to casting temperature. Higher temperatures will result in greater shrinkage as the bullet cools and produce a slightly smaller and lighter bullet than one cast of the same alloy at a lower temperature.

http://www.lasc.us/

[Leftoverdj]

It's the proportion of antimony and tin to lead that determines the as cast weight. Your alloy is very high in lead so it casts heavy. Were you to aircool those bullets, they would would be quite soft, but they would still weigh the same.

[Jon K]

SSB,

The label weight the manufacturer gives to a mold is only an estimate, and your alloy and technics of pouring will vary the weight. And sometimes no matter what you do thhe weight will never come out to match the label, just keep in mind the labeled weight is only an estimate.

More important than the weight matching the label, is how well it shoots.

Have Fun Shooting,
Jon

[montana_charlie]

The weight a particular mould will throw is also dependant on the alloy the manufacture uses as a standard. Lyman moulds are 'standardized' to Lyman #2 alloy.
I don't know what Lee uses...but something in the back of my mind keeps whispering 'linotype'.
CM

[mooman76]

Lee uses pure lead for the bullet moulds that apply but I think they use something else for regular moulds!

[44man]

John, casting hotter would result in a larger boolit because the mold expands more.
SSB, that small amount of difference in weight is nothing. Even if you used the alloy the mold was regulated for, you would be hard pressed to get the weight as stated. 15, 20, even 30 gr's is common. Forget it and shoot them. Every alloy will throw a different weight and the closer to pure lead you get, the more they will weigh. It makes no difference in the powder charge at all.

[klausg]

mc/mooman-
IIRC Lee uses 10/1 alloy.

-Klaus

[rebliss]

John, casting hotter would result in a larger boolit because the mold expands more.

OK, just to be sure, a hotter alloy will yield larger boolits? What if the mould is not up to max temp yet, but is still filling out? Does the alloy contract as it cools? Does WQ cause a boolit to size larger than AC?

I'm very interested in this because I've got a mould that's throwing very close to the diameter I want to size to, and would like to ensure I get an even size.

Thanks.

[44man]

The measurement increase is not much with a very hot mold, you might gain .0005"or less. The metal contracts when it cools of course or you would not get the boolits out of the mold. Unless you are really needing the extra diameter, you will not notice anything at all.
Harder alloys will grow larger as they age, again it is not a big deal. Water dropping makes them harder and I do it because it makes casting easier.
The important thing is to see if you really need to size your boolits. Most of the time they shoot better as cast. What you have to look for with Ruger .45's is to see if the throats are the right size. They made a lot of guns with throats too small. You need throats .0005 to .001 over bore size for the best accuracy. Even a tad larger won't hurt but if the throats are smaller then the bore you will have a problem.
You should slug the bore and throats to see what you have. If you can push a .452 cast boolit through the throat with your thumb you should be good. Try a jacketed bullet and see if it will go through.
First is to get the measurements before you do anything else. If your bore is .452 and the throats are .450 or .451, nothing will shoot good.