The first thing that comes to mind, is to use one of your moulds and cast several batches of well filled and formed bullets using a known ally, then cast the same number of bullets using a different alloy and so on until you have exhausted the range of alloys you may be intending to use.

Then measure the dimensions of the mold and then check that dimension against each batch of bullets you have cast. You should then have a reasonable idea of how the various alloys shrink on cooling.

Harry

JESSE:
    I have always used a factor of 0.6% for both iron and aluminum blocks with lead/tin alloys.
     This is subject to calculation -- get out a handbook(1)and look up the coeff'ts of thermal expansion of lead, aluminum, and iron.   Guesstimate the temperature of the blocks which will not be far from the melting point of the alloy.  Blocks and bullets will be close to the same temperature when the bullet solidifies.   Then calculate how much the bullet shrinks when it cools.    Also calculate how much the blocks shrink when they cool.   Then you will see how much smaller a room-temperature bullet is than the room-temp blocks.
   Or, as HARRY suggests, cast some bullets and compare their diameter to that of the cavities.   You may have to make plug gauges to get a good measure of, e.g., the base-band.

(1) I always keep a copy of the "Handbook of Chemistry and Physics" Chemical Rubber Publishing Co. around.  They can often be found for a couple of bucks in used-book stores.  The older 4 !/2 x 7 format editions have more useful old-time information in them.

CHRIS
RGChristensen

frnkeore wrote on Jun 15^th, 2014 at 3:20pm:

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Scroll down to Alloy shrinkage of cast bullets

Look at this side and scroll app. half way down, left side:

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That will tell you all about bullet shrinkage.

   As I said, the LASC site has some interesting numbers, but aside from getting you in the ball part, they don't tell much.  Note that it makes a difference what the BLOCKS are made of, how much "shrinkage" you get.   

CHRIS
RGChristensen