Originally Posted by
DR Owl Creek
Are you sure you have your decimal point in the right place? Most people using Cu enhanced alloys have a really hard time casting with those alloys once the Cu content goes much higher than .5%, unless the run their alloy and mould temperatures very high. The Cu acts as a "grain refiner", much like As, but too much Cu in the alloy can make casting almost impossible, because of the rapid cooling of the Cu (melting point 1984 degress F) causes the Cu that's in the alloy to freeze out of solution. This causes "sheeting" around the nozzle of bottom pout pots, and can even cause "sheeting" within the mould when pouring with a ladle.
As far as the Sn being equal to the Sb in the alloy, is that they form the intermetallic compound SbSn. The intermetallic compound SbSn will mix in solution with the Pb, as long as the content doesn't exceed about 3.5% to 5%. Any Sn exceeding the amount of Sb will not form into SbSn, and simply mix into the Pb. That portion of PbSn will not harden and remain soft. Also, any amount of Sb not formed into the compound SbSn will solidify before the Pb does, and create spots of that element within the bullet. Those spots of Sb within a cast bullet will create imbalances as the Sb is not as dense as Pb. That's why too much Sn above the Sb can be detrimental to achieving high velocity with a cast bullet.
Finally, as far as being able to push a cast bullet at high velocity, that's one thing, but actually being able to hit something with it is another. IMO
Dave