Frosty and shiny on same boolits.

[Dadswickedammo]

So last nite cast about 600 .312 155gr 6 cavity mold 5lb super hard 12lb pure.
Mix is approx. Pot temp about 650.
Boolits cast very nice but some all shinny some all frosty and some mix.
All I can think is my mix not well mixed or mold temp. It's not a function problem I just like all the same.

[OS OK]

I think your mold went over-temp. if your pot temp. is correct.

Did you actually measure the pot temp. or use a PID control?

It makes it hard to estimate problems without empirical measurements...

[BK7saum]

I think sometimes a part of the mold can be hotter. Middle cavities versus end cavities, or middle of mold vs bottom of mold (drive bands vs nose of boolit ). That and mold temp and pot temp are right at that temp between shiny and frosty.

[BK7saum]

Lee 6 cavity Aluminum mold?

[popper]

Normal for Al moulds and rifle boolits. You could slow down to make them shiny all the way. Don't have any idea why you want that much Sb in your alloy. 1.5# S.H. should give you COWW.

[Phlier]

You need a bit of tin in that mix, especially with that much antimony. Adding tin increases the lead's ability to keep antimony dissolved into the alloy. But yeah, that's a lot more antimony than what you need. With that much antimony (and no tin), you'll get frosty boolits at a lower mold temp than you'd normally start getting them at, especially with no tin. You're running 8.38% antimony. That's a lot.

If you only read a couple of pages of From Ingot to Target: A Cast Bullet Guide for Handguns, make it the section on bullet alloys. It starts on page 27: http://www.lasc.us/Fryxell_Book_textonly2.pdf

Here's a very user friendly alloy calculator: https://docs.google.com/spreadsheets/d/1LoKxRMJ8fWRtECST-PXrWRS80QzoONVJzMLmJLS18fM/edit#gid=808458930 To use it, put the weight of each metal type in the appropriate boxes, then read the results at the bottom. The results will show the percentages of tin, antimony, and lead.

[Oklahoma Rebel]

you could add 1/3 the weight in pure lead+ 2% tin.. maybe 3% and still have very hard boolits that would work well in any rifle. those u have now will shatter and crumble when they hit something

[runfiverun]

I look for that light frosting in the center of some of my aluminum molds.
with my accurate 165-A I want that light frost color on the middle of the boolit, seeing that tells me I am holding my mold temp in a consistent window.
it's also the point between breaking out the sprue cut, and getting a nub.

[RogerDat]

Aside from the unusually hard alloy you have making a difference, for my casting and alloy I try for right at the edge of frosty. So some are mostly shiny and some are a bit more frosty. Most molds this point in mold temperature seems to produce good bullets.

[Dadswickedammo]

So this is me second big casting and still twerking the mix may be a bit hard next go around lil less antimony. And still working temps out using a thermometer.

[runfiverun]

the visual clue from the mold is all you need to know.
your alloy can be 625 or 770 and you can get the same exact results from your mold.

[rintinglen]

I have no issue with mildly frosty, nor do I have much of one with shiny and bright, but mixed boolits often are a bit undersized in the middle where the blocks have become a bit too hot. Super frosty will very likely be small, shoot poorly and lead like crazy. I have the T-shirt.