Question about cu enriched alloy?

[RickinTN]

Hello all,
I've read the threads about enriching alloys with copper for increased velocity and toughness. If my math is correct, and I believe it is, I have the components to mix a batch of 3.44% sb, 3.71% sn and .4% cu. I have not yet melted the mix
I have two questions:
#1 Is the .4% cu too much? In my mind I think I remember most folks using somewhere in the .25% range but my rememberer isn't what it once was.

#2 My goal is to have the sb and cu content equal the sn content, as I think is suggested, and I'm off by .13%. Is this critical or am I trying to seperate the fly droppings from the black pepper? My source for tin in this instance is 95-5 solder with the 5% being cu, so if I up the tin content I'm also upping the cu content, which takes me back to question #1.

I'm comfortable I have enough as for heat treating as 80% of my alloy is from a mix of magnum and chilled shot, but the test equipment wasn't set up to detect it. The rest is from range scrap and Monotype. I usually heat treat @ 425 degrees and water drop. I'm thinking this should work well in lieu of water dropping from the mold.

For those that are familiar with cu enrichment what are your thoughts and/or ideas?

Thanks in advance,
Rick

[popper]

Cu alloys with Sb & Sn, Cu replaces lead atoms in the lattice, which is what you want. Any Cu > 0.4% will precipitate out of the lead and combine with the Sb or Sn (it will form Cu2Sb and some SnCu combination). Just think of the Sb & Sn sucking up the excess Cu. SbCu is stronger than SnCu and doesn't dendrite. As goes into the Pb and keeps the SbCu grains small. Try it without the tin, you will like it. I would keep the pot temp maybe 50F above the liquid temp or just enough so the pour is good and the spout doesn't freeze. Let it cook for 1/2 hr & stir often before casting. I H-T rather than W-D.

sb and cu content equal the sn content This doesn't figure. Lead will take 0.3% (when solid), Sb takes 2x the Sb% and SnCu has a bunch of compounds, like Sb6Cu3 and the Sb & Sn reactions occur before the Pb/Cu so you may not get any Cu in the lead.