Questions about mould drop sizes & sizers

[.41LC]

When a mould lists ".430" nominal diameter" what does that mean? Will it drop smaller or larger most of the time, and by how much?

Can bullet sizers make a bullet larger?

[montana_charlie]

It means the mould will cast a .430" diameter bullet if you use the same alloy, and the same casting temperature, the mould is made for...with a caveat.

That is the part where some mould makers state that finished diameter may be as much as (say) .002" larger than nominal. When you see that, it will usually be a maker who uses a cherry to cut the cavity. His cherry is made a little large so it can be resharpened a certain number of times. As it gets resharpened, it gets smaller.
When it's new, it cuts the cavity a little over nominal. After it's been resharpened enough times to become too small, it's replaced with a new one.

Lathe bored moulds will usually be cut to produce right at nominal diameter when the company's 'standard' alloy is used. If you cast with a different mix, you can expect a different result. Lyman's standard is Lyman #2 alloy. Somebody once said Lee's standard is wheelweight metal. I don't know if that's true, but wheelweights are highly variable...so it sounds like a bad idea to me.

If you order a mould from a custom maker, he will often ask what alloy you intend to use. Then, he will adjust the cavity size to meet your requirement when using that alloy.

A bullet sizing die can only make a bullet smaller when it's used as designed.

CM

[.41LC]

What if you cast with pure lead, would you generally get larger or smaller bullets?

[Maven]

Slightly smaller diameter, but also heavier CB's from pure Pb.

[mooman76]

Smaller with pure lead but moulds designed to drop pure lead should be larger to accomidate that.