I've got a bunch of cast bullets at 25:1 in inventory. Just switched to 20:1 for new bullets (same mould). Purpose: to reduce leading with increased velocity. If all my bullets are segregated by .1gr weight, can I use up the old supply (of bullets) mixed with the new if they are of equal weights? Or should I melt down the old bullets and add a proportionate amount of tin to make the "melt" 20:1? (Seems like an awful lot of fuss.)

    If you had a 25:1 bullet that weighed the same as a 20:1 bullet from the same mould, the 25:1 bullet would be seriously defective.  It would be missing some metal SOMEWHERE, since the bulk densities are different.

CHRIS
RGChristensen

Chris is right on this.  There will be a difference in weight based on alloy but,,,remember the difference will be smaller then you might think, possible only a few grains based on the size and weight of the bullet being cast.  So knowing what a good bullet at a given alloy 'should weigh' is essential.  And as Frank says you may notice little if any difference between the two 'at the target' but you should stick with one alloy per target.
Of course remelting and alloying is a possibility, but a huge pain.

Cary

In my experience, the alloy has less to do with weight variations than the temperature of both the alloy and mould blocks.  Also, weight will vary if the dipper is held on the mould block for more time, in other words the casting is done at a slower pace.

Keep on hav'n fun!
MikeT