What causes this casting flaw?

[geargnasher]

What's your alloy's "full liquidus" point?

Gear

[Iron Mike Golf]

Base edges don't look sharp. Is it a plain base mold?

[runfiverun]

a master caster is a whole different thing than hand casting.
you can adjust the guides so that the mold is slightly off to the side.
what i'd do is cast a bit quicker and don't turn on the cooling fan till you have about 50 pours into a run, then maintain your pace.
you are most likely waiting till the sprue color changes then doing the count.
forget that, just run the thing, the fan will help keep the mold cool enough to not get frosty boolits.
find the molds happy temp and pace the casting/fan blowing on the mold, to that.
you might need to adjust the sprue tension a little.
but i would work on mold temp first,sprue tension second,and then the swirl pour and venting last.
for the smaller 38 etc size boolits i usually run my pot right near 725=730 and just kept a steady pace.
looking for a satin grey boolit color

[old_haidouk]

Magma was right. They said the lead was too hot and it was being sucked out of the base. I called them today and they said to lower the temp on the alloy. I did down to about 635 on the PID. And beautiful bullets started dropping out. I just can't figure out why two parts isotope and one part lyno alloy would like a much lower temp?...

[williamwaco]

I am on board with the pour being the problem.
EVERY mold is an individual. They all want something different.

When you find out how to make that mold work, start a page in your reloading notebook for molds. Record the mold and what makes it work. Record the alloy content, the alloy temperature, the pouring method, how long to wait before cutting sprue and if or how you lubricated the sprue plate and anything else you had to do to make it work.

I promise you that if you cast a large batch of bullets, when you get that mold out next time, you will not remember how to make it work and you will have to figure it out again.

Pouring fast is always a problem. I find that if I adjust the stream volume low enough that it takes two to three seconds to fill the cavity and create a large sprue puddle, these problems will usually go away. Many molds will not work well with the stream entering the center of the sprue hole straight down. ( some work OK that way )

Large sprue puddle means anywhere from the size of a nickle to the size of a quarter and slightly less than 1/8" thick.

I use Geargnashers swirling technique and find it really helps.

[canyon-ghost]

Antimony and tin, unlike lead, have a higher melting point but, like a solution of salt and water, a much lower melting point when alloyed.

Compounds in a solution act differently than the two would seperately.

[Sonnypie]

... it's permanently ugly at best. Sitting down helps too.

Gear

On another note, I've known some gals like that.
Sitting down didn't work as well as closing my eyes though.

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Carry on....

[Sonnypie]

If you put a gas check on it, nobody will know.

[runfiverun]

see post 21.
that's why it worked.
you have a high tin, high antimony alloy, it melts at a lower temp.
fills out well but cools to hard faster the higher temp created uneven cooling speeds between the sprue and the boolit in the mold.
the sprue was cooling faster than the boolit that was trying to suck the lead in.