Good Mold Dropping undersized Boolits

[Eddie1971]

Hey guys, I have this one mold that seems to be dropping undersized boolits, like .001-.002 smaller than advertised. The other ones from the same maker have dropped on target from day one with the same alloy. In fact I used a few of them in the same session with the same alloy. Any ideas? Could it possibly be that this requires a longer break in period than the others? Thanks!

[243winxb]

Different day=Different mold.

What alloy is the mold regulated for? Antimony makes as cast bullets larger.

LEE - Our bullet mold weights for our rifle and pistol bullet molds are based in a 95% Lead / 5% Tin mixture.

[Targa]

https://youtu.be/3GTTeXHVYWc Here is a good video by Mr. Fortunecookie in reference to adjusting cast bullet size.

[JonB_in_Glencoe]

like .001-.002 smaller than advertised.

>>>SNIP

It happens.
It is the way the mold was cut, there is probably nothing you can do about the mold itself.

with that said,
sometimes, you can get boolits about .001 larger by using a alloy with more Antimony content and casting as cold (shiny) as possible. I have one Lyman mold that drops a boolit with a GC shank that is a hair large for GCs to ft nicely, so I cast with that one as HOT (frosty) as possible with a alloy with low antimony content, and the boolits drop smaller. I mention that, in case your typical technique is to cast hot frosty boolits...if you can reduce the frost by casting colder, you should see larger boolits.

[longbow]

You don't mention the brand of mould.

In my experience my old Lyman moulds cast slightly large using ACWW where newer Lyman moulds seem to cast undersize using ACWW. Lyman cuts cavities to suit their #2 alloy.

Other moulds I have... Accurate, Muhec and NOE all cast about 0.001" over spec using ACWW but they were ordered to suit ACWW.

As mentioned a change of alloy might increase diameter by a thou or so.

Alternately you can Beagle the mould to get up to about 0.003" larger boolits.

You could lap it to increase diameter as well but that takes some work and if you aren't careful you can make the cavities oval.

Is the mould new and casting under spec'd diameter? If so the maker should fix it.

Longbow

[Conditor22]

+1 on not using the alloy the mold was made for.

try adding a little tin to aid fill out (if needed) and casting around 650 - 680° [harder alloys melt at lower temperatures]

push comes to shove you could polish your mold to get it to drop larger or

PC the boolits to gain some diamiter