Brittle Sprue?!?

[BNE]

NEWBIE question:

I made a mix today of the following:
93.5% Lead
4.3% Antimony
2.1% Tin

I used WW for most of this. I was careful to sort the WW and then to monitor the temp to makesure that I was not going to melt Zn if any got into the mix.
I added one pound of Linotype that I melted down from strips.
I used a 60 / 40 solder to increase the tin percentage.

So I think my mix was clean, but I noticed the sprues were brittle. They would break into small pieces when I knocked them off. The bullets looked OK and I even took one and hammered it to make sure it was not brittle. It held together even after multiple hits.

Why is this? Too much tin? Antimony?

Should I be worried?

Any advice would be greatly appreciated.

[Bent Ramrod]

That is a very common phenomenon with highly alloyed lead. I can knock the entire sprue off the plate sometimes by tapping the mould handles just after it has hardened. Shouldn't be any problem at room temperature.

I have a double cavity 40392 that overheats quickly. The boolits have to cool in the mould for extra time or they will "chip" or crack as they are being removed if the alloy has antimony in it. The ones that survive intact shoot fine.

[45 acp]

I would say the mold/sprue plate are too hot.

[41 mag fan]

too much antimony. I would think 2% would be optimum on it.

[rockshooter]

mold too hot (well, plate) too hot. I get the same thing with 20:1. Not a problem as long as bases not being ripped.
Loren

[btroj]

Not a big deal.
That is a pretty rich alloy, what are you shooting it in?

[44man]

Merely a time to cut thing. If I am running along good and get little pits in the center of the base I ignore them. They have never harmed a thing in my revolvers.
Now those itty bitty boolits?

[BNE]

Thanks guys. I am making .45s. I have access to an X-ray Fluorescence machine at work and have been able to confirm that the mix was what I thought it was. No Zinc. It just seemed wrong. This was only my second real casting session.

I had read so much about the fact that iron molds take longer to heat up, that I guess I overheated. Thanks for the input.

[badbob454]

the sprue lead will aerate and fall apart ..break if .removed while it is in a plastic stage (semi fluid) the boolits should be left in the mold to cool a few seconds after cutting a sprue this hot . i have had this common experience myself , keep on ... you will do good...
i cast with 2 different bullet molds for this reason , i can cast more boolits and i dont have to wait to cut the sprue