What causes acne in cast bullets?

[Jtarm]

I cast a few-hundred 10mm bullets today and roughly have came out with what I can only describe as acne:

https://uploads.tapatalk-cdn.com/20211024/2251dcef576edd0bf02753db211272e6.jpg

They filled out well. This in a brand-new RCBS Pro Melt 2.

The alloy is COWW + 2, smelted, cleaned, and fluxed in a separate pot, then fluxed again the the furnace.

[Winger Ed.]

I'd raise the heat a bit, and not be bashfull about stirring every few minutes.

I have good luck with a hot mold, and raise the heat up until I get a bit of frosting, then back it off a little.

I heat my Promelt a 1/2 hour or so with the mold resting over the top, and turned up almost as high as it will go.
I get a few poorly filled out rejects, but not many before the mold gets really hot, then I can watch for the frost.

As I rock along, and if I start getting frost again, I just slow down my rate between pot, and drop.
I do get the slightest little shrink hole at the sprue cut off, but it doesn't bother me.

[nhyrum]

Yeah, looks cold to me


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[cwlongshot]

Mix your alloy in the pot more.
Run 700-730 degrees.
Start with a 400 degree mold.
Flush your mold with brake clean.

Good luck
CW

[Jtarm]

Muchas gracias gents!

[white eagle]

looks like a mold not ready to cast yet
not hot enough or has not been seasoned yet
which is cast with enough that it drops nice boolits
normally they break in or season within the second or third session

[JSnover]

Looks maybe a little cool and maybe a little contamination in the cavity. Do all of them come out with that same funky spot in the same location?

[gwpercle]

What Winger Ed said about raising the heat and don't be bashful about stirring ...
Stir with a little wooden stick / paddle and let it char as you stir slowly ... this is a mini-flux and goes a long way to getting good boolits . Flux good when you start and flux again when the pot is halfway full . Depending on pot size the 2nd flux may be omitted if enough wood paddle gets charred into the mix.
Gary

[fredj338]

Flux more often. I run about 730deg & stir the casting pot with a wooden paint stick often.