Alloy and Cast size question

[hylander]

Dumb question here :oops:
I have been casting with COWW for just about everything.
However I would like to cast some pistol bullets a bit softer.
I'm thinking 1 part pure lead to 2 parts COWW.
Will this effect my as cast size, will the bullets drop larger or drop smaller ?

[62chevy]

Slightly smaller depending on mold temp. More Sb usually means bigger but like I said depends on mold temp.

[scottfire1957]

Simple answer is yes. Do a few and measure them.

[runfiverun]

yeah but not realy enough to matter unleass your on the ragged edge of diameter and .0005 is gonna throw you off.
you can manipulate other things like mold and alloy to temp to help gain that back though if you really need it.

[lobogunleather]

I started casting pistol bullets about 1972, using primarily used wheel weights. In the early 1980's I started casting rifle bullets and getting pretty serious about accuracy and performance on game animals, etc, so I got into linotype metal. I tried several alloys with various blends of wheel weights and linotype for different applications. One of the first things I noticed was a measurable difference in as-cast diameters, with the harder alloys being significantly larger than the softer. One of the other effects was changes in bullet weights due to different proportions of the metals.

Most bullet molds are described using Lyman #2 alloy as the base point, establishing the base dimensions (including diameter) and base weight. As we change alloys we can expect changes in dimensions and weight, with the harder alloys generally shrinking less and weighing less.

One example I specifically recall because I have used so many of them is the Lee C309-180, a .30 caliber 180-grain round nose gas check bullet. Cast in straight wheel weights I had as-cast diameter of .3084" and weight of 172 grains. Cast in straight linotype metal I got as-cast diameter of .3092" and weight of 166 grains.

Alloys will vary widely depending on several factors, each mold is likely to be a law unto itself, and individual practices are likely to have an effect as well. Probably no hard and fast rule or tables to go by, just trial and error to achieve what you need for a particular firearm.

[62chevy]

One example I specifically recall because I have used so many of them is the Lee C309-180, a .30 caliber 180-grain round nose gas check bullet. Cast in straight wheel weights I had as-cast diameter of .3084" and weight of 172 grains. Cast in straight linotype metal I got as-cast diameter of .3092" and weight of 166 grains.

Funny that mold is doing the same for me but all my other Lee molds are heavy for stated weight.

[Deadpool]

Adding some Bismuth will increase size (somewhat counter the shrink mentioned above) and also help keep the hardness down.

[ioon44]

What will the effect of Bismuth be as to the boolit mold filling out?

[runfiverun]

nothing really.
in small amounts it acts just like antimony.
it will add hardness of course, but bismuth is also brittle keep the amounts low.