What causes this?

[long_arm]

Intermittent problem casting today. Mold is a single cavity Ideal 429-421, alloy 3:1 lead:lino.
The pic isn't great, sorry. But can you see the broken shoulder of the front driving band? It only seemed to happen once in awhile..

https://i.postimg.cc/brFPzZCm/PXL-20220307-190129173.jpg (https://postimg.cc/GTYVKm1D)

[BK7saum]

Emptying the mold before the boolit hardens. the square lube grooves with minimal draft will crack the shoulder sometimes.

[long_arm]

Most turned out reasonably well. I don't know the cause, or understand the intermittent aspect of the problem
https://i.postimg.cc/pV9RZZp7/PXL-20220306-222137648.jpg (https://postimg.cc/RqzkCw1Q)what do betta fish need (https://bettafishcaretaker.com/supplies)

[long_arm]

Hey thank you BK7saum!

[Winger Ed.]

I always expect a little bit of a reject rate.
It seems like the taller the boolit, the more prone they are to something being amiss.
As long as it's just a couple percent-- I'd rock on.

[gwpercle]

I get that every now and then also ... and call it incomplete fill out . But actually it might be a little dross inclusion in the driving band edge , it seems to be in line with more inclusion on the boolit nose above it ...someone without glaucoma needs to look at the photo ...
If these edges are small I ignore them but if they keep happening I will stop and flux the pot well .
Fluxing and skimming will usually solve the problem ...whatever it is .

By the way ... Sweet Looking Boolits ...Elmer would like those !
Gary

[quilbilly]

I have that mold, too. I would add a little bit of tin as well.

[long_arm]

Fluxing and skimming: check.
Tin: also, check. Forgot to mention it in my first post .

I would find it easy to believe that i need to wait a bit longer before dropping the bullet. As it is a single cavity mold i was feeling like I needed to hustle .. thanks again for the reminders

[Bazoo]

It looks like a bit of frosting starting at the sharp edges. That is incomplete fillout caused from not having a large enough sprue puddle.

[long_arm]

Bazoo,
Thanks again for the tip. Will remember that tomorrow

[Winger Ed.]

As it is a single cavity mold i was feeling like I needed to hustle

I tend to run my pot a little on the hot side.
As a filled mold come out from under the spout, I let the mold block drop and tap
on a piece of soft wood right there in front of the spout.

It might be my imagination, but I think the little bump while its still molten helps the fill out.
When the sprue turns dull, then about a second or two later I open & drop.

It works for me doing .38cal 148DEWCs to 405s in .45cal. in Iron molds.

[long_arm]

Winger, that's interesting. Will give it a go. Thank you

[BK7saum]

i have found that casting 525 grain boolits with a bottom pour i get rounded driving bands unless i keep the pour running and let the lead stream run across the sprue hole for an additional 2 to 3 seconds (similar to how folks ladle). It has been working great. i have a lot less rejects due to rounded bands and incomplete fillout. This is with a brass mold.