Wrong mould number?

[VEARL]

I used my mic on some 490 RB that I molded last week. They are all showing a diam. of .473 to .474 .
The Lyman mould is stamped .490 RB. Used soft lead in the moulds.
Can't figure out why they are turning out smaller than .490.
Anyone have an explanation?

 

[bpd303]

I presume you are using pure soft lead. Alloy's will shrink more than soft. Other than that the mold could be mis-marked.

 

[Jim Blair]

From my experience with Lyman molds they base their sizing on using the No.2 Bullet alloy-

Lyman #2 Bullet Casting Alloy (90% Lead, 5% Tin, 5% Antimony)

I would call Lyman and explain your problem,they've always had pretty good customer service.Molds get messed up,cherries wear with use.

 

[George T.]

Yeah my thought was that you may not be using pure lead. That is quite a lot of shrinkage. A call to Lyman mat get you a replacement. Geo. T.

 

[Bon Sauvage]

Hmmm......my experience is that pure lead always shrinks more then alloyed lead.

 

[russecv58]

with that much of a difference, I would say the mold was marked wrong. using alloys would not cause anywhere near that much shrinkage.

 

[Jim Blair]

After a little checking Lyman does calibrate their mold sizes using a Lyman No.2 bullet alloy.Using a straight lead or pure lead will cast a smaller ball due to shrinkage factors.I doubt it is marked wrong if it is a newer mold,the next smaller size is .457,the next size up is .495.You might try adding some tin or 50/50 solder to reduce the shrinkage.The heat at which you're casting may also be a factor.

 

[paulab]

in my experience, the difference in shrinkage between 30:1 and pure lead is only one half of a thousandth [.0005]

 

[bpd303]

Hmmm......my experience is that pure lead always shrinks more then alloyed lead.

You're absolutely right. I got it backwards, hate it when that happens.

So that only leaves two possibilities (1)mis-marked mold or (2)mis calibrated mic.

I remember one time when using a dial caliper and checking the length of some 577/450 cases, somehow the dial was moved way off zero and made me crazy until I figured it out.