Is it Zinc?

[Irascible]

I had a batch of unknown alloy in someones ingots. About 2 months ago, I smelted it all down together and while I was at it cast a few bullets to check hardness. It seemed to cast well, but I didn't pay too much attention as all I wanted was hardness numbers to give me some idea of what it is. The hardness was checked every few days and then weeks and got up to about 11 a month ago and 12 today. It seemed to be clip on wheel weight alloy. So, to the 10 1/2 pounds, I added 2 1/2 of pure lead and 3 pounds of an alloy which was 8 lbs of ww to 2 lbs of pure + 3% tin. I then heated it to 550 deg and fluxed and stirred and fluxed and stirred. I moved the temp knob to 800 deg and set the mould on top. As soon as the light went off, I turned the heat back to 700 and started casting. The first casts from the brass MP 45 cal 278gr mould were bright shiney and a little wrinkled as expected. Once the mould got hot the bullets came out with a light frost and I cast about 100 bullets. Interestingly, the light frost became a heavy frost as the bullets cooled? I kept going until I had 100 on the towel. I then grabbed the coolest ones and set them on the electronic scale. What? I then checked a bunch more. All were about 10% light, heavily frosted, BNH of 15(as soon as they cooled) and a 70% rejection rate for weight discrepency. But, they all looked good and were about the right diameter! Oh **** I thought I got a good load of Zinc. I remelted all the rejects and poured ingots for the scrap man.
SO, does it sound like Zinc? I kept the 33 heaviest bullets (253gr) and am interested in shooting them IF it won't cause a problem. What do you think?

[runfiverun]

not zinc.
it's temperature variation betwen your alloy slowly cooling down and your mold heating up and changing your cavity size.
you now know another way to not cast good boolits.

[Irascible]

I cast the same way that I usually do with my normal alloy of 8ww to 2 lead + 2% to 3% tin. I usually have a reject rate of less than 10%. I don't think a slight change in cavity size can make a 10% lighter bullet, 278gr down to 253gr! And, how can one explain the frosting? I guess I'll have to find some sulphuric acid to test it. Or is it Muriatic?

[cbrick]

But, they all looked good and were about the right diameter! SO, does it sound like Zinc? What do you think?

I think R5R is right . . . NOT zinc.

R5R could also be right about the temp variation. In addition, that's quite the cocktail of alloy's, are you certain that it was completely blended into one homogenous melt? In other words, how well did you flux and what did you flux with?

Your right, that's a lot of weight variation but it's pretty doubtful from what you told us that it's zinc.

Rick

[Irascible]

Hmmm, maybe it's some kind of babbit or pewter. You are right it was some kind of mix, but I hated to throw out 10 1/2 pounds of alloy, so I thought I would just add a little tin via the remnants of another batch and soften it up some to get closer to what I usually shoot and use the bullets for plinking and as long as they didn/t lead, I didn't care. I guess I just wasted the pure lead and the remnants of my usual batch.
I'm glad I didn't pay for any of this :>). Now I get to throw out 16 pounds of ?
Oh stirred well and fluxed a few times with NEI flakes, which I think is some kind of rosin (resin?)

[cbrick]

not zinc.
it's temperature variation betwen your alloy slowly cooling down and your mold heating up and changing your cavity size.
you now know another way to not cast good boolits.

Pay attention to this before you throw anything away. Yes, a wide variation in casting temps, both mold and alloy much less both will make quite the difference in as cast weights.

Experiment, you may be surprised.

Rick

[shadygrady]

if you got zinc send it to me

[40Super]

I've learned to let my pot sit at my casting temp for 5 minutes or so and stir good with a little flux to make sure all alloys are completely mixed(especially if adding an ingot of pure or tin ,ect..) that way everytime I cast they come out consistant. I used to have an occasional 5-8gr difference in weights before I made sure to have everything at the same temp and mixed well. Don't throw it away, it is probably good lead and may just need more pure to soften it up,plus it will bring the weight up.

[glicerin]

Light bullets, good fill and frosted sounds like an accidental surplus of tin or antimony. If antimony-very hard(try a crush test with normal bullet in vise).

[Irascible]

I checked the hardness again. It is now 3 days and it's virtually the same 14 1/2 to 15. The nice shiney bands are still nice and shiney from sizing. The rest of the bullet is still heavily frosted.
I cast a bunch of 8 to 2 + 2% today in the same moulds using all the same procedures and everything came out well. As usual! Good fill out and the bullets increased about 1gr as the mould got to full heat