Cast RBs shrinking?

[SaltyJim]

Is it normal for RBs to shrink?

I am casting pure lead (BHN5) round balls in an old Ideal mold marked 451 but they drop at 447/448. I know it's only a few thousandths but I am planning to shoot them from my Pietta 1858 Remington NMA revolver which recommends 451.

[waksupi]

That's quite a variation. Some molds just plain don't cast what they are marked as. Use a different mold that you know the cast size, and see if you alloy casts to the same diameter as expected. If so, it's an undersized RB mold. You may be able to lap it out to desired dimension.

[HWooldridge]

Pure lead shrinks more than alloys - which is why a moldmaker needs to know the intended alloy when a mold is ordered.

[SaltyJim]

Pure lead shrinks more than alloys - which is why a moldmaker needs to know the intended alloy when a mold is ordered.

Thank you HWooldridge that explains why my 440 mold drops 438 balls too