quicksylver
Well-Known Member
This happens with all my long nose bore riders.I think it is excessive mold heat, your opinion?
What Causes This?
- Thread starter quicksylver
- Start date
This happens with all my long nose bore riders.I think it is excessive mold heat, your opinion?
yodogsandman
Well-Known Member
I'm not quite sure what you're showing us. Are the bore riding sections being pulled like taffy? If so, I'd recommend waiting a few seconds after cutting the sprue to open your mold.
quicksylver
Well-Known Member
Hey thanks for the reply. To answer the question ,no. I'be casting along fine and then these voids start to appear. Let the mold cool slightly and they are gone .
RicinYakima
High Steppes of Eastern Washington
OK, I will write, even though I have no proof, but just experience. I have had this for a couple of years in the early "00s. I THINK this is a condition of a couple of things. Tin content is above antimony content: i.e. antimony is less than 5% and tin content is greater than the antimony content. This happened to me several times when I thought I did not have enough tin and kept adding tin to the melt. When you are in this unbalanced situation, the antimony is crystalizing before the cavity is full. It is localize by the hottest spot on the cavity surface. I cured my mould by letting it cool, added 25% WW's that were 2.5% antimony and 0.1% tin, and restarting. This worked several times for me, but I don't guarantee anything.
I have had problems with excessive heat causing issues but always with large diameter, heavy bullets. Never that extreme.
I think, heavy on the think, I have heard of a situation similar to what Ric mentioned. Too much tin causing flaws like that from a really hot mould.
What alloy are you using?
I think, heavy on the think, I have heard of a situation similar to what Ric mentioned. Too much tin causing flaws like that from a really hot mould.
What alloy are you using?
yodogsandman
Well-Known Member
That happened to me, also. Before I used a PID, any way. The alloy temperature is too hot. It would only show on one side of the mold, too. Looked like inclusions from dirty alloy. I didn't know the temperature so, I would turn down the pot a notch, throw in some sprues and leave the mold open a few seconds after dumping the bullets to allow that to cool in between. just in case it was the mold too hot. Whatever I did, it worked to stop and prevent it from happening any more. It seemed to happen when running the casting rhythm at full warp speed to heat the mold up to temperature. That was before using a hot plate to warm the mold, too. After the problem solved itself, I'd turn the pot back up and cast with my normal cadence, tossing the sprue or culls back in for each cast.
Ian
Notorious member
Your mould is about a hundred degrees too cold and the alloy shrinks radically as it's crash-cooled during the fill. Try casting faster, MUCH faster until your bullets get a light, even frost all over and your problem will be solved, along with your rounded base bands and wrinkles, and the voids you can't see.
KHornet
Well-Known Member
After looking at the picture more closely, I agree with Ian. I like a lite frost all over the bullet. Far better that a bit to hot tha Paco Kelly said one time that he felt that some frost was helpful in holding in hard lube. Not sure if that is correct, but I like Paco's articles, cause, to me they usually made sense.
Ian
Notorious member
I like the mould just hot enough to leave a light, satin frost with alloy that contains at least 2% Sb. With much less Sb than that, the bullets will be fairly shiny no matter what. I've read both PK's and Richard Lee's comments about lube adhesion being better with frosty bullets, but if you have just a light haze that will wipe right off with a dry rag, revealing a very shiny, smooth surface beneath, I don't see it aiding lube retention much, but who knows. The "frost" certainly doesn't hurt anything unless the mould is run hot enough to make a permanently dull surface on the bullet. If the mould is too hot then excess shrinkage, rounded bands, and undersized bullets typically result.
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JonB
Halcyon member
I use to get that very often with long bullets. I called it "shrinkage", I'm not sure if that is the correct term or not?
I got shrinkage whether the mold was hot enough to make lightly frosted "Grey" bullets or if the mold was colder like your mold obviously was when casting the more shiney bullets in your photo. I wrote a long post about it on another forum.
http://castboolits.gunloads.com/sho...ncing-the-solution-(for-me-anyway)&highlight=
from that link:
"The Solution: Pouring as large of a sprue puddle as reasonably possible.
My problem I had to overcome to resolve this:
I'm sure I've read about pouring a large sprue and I'm sure I've been told that as well, when I asked about shrinkage in the past. But what it always came down to is...when I'd get into a comfortable pouring rhythm, I pour a smaller and smaller sprue...so as to reduce the amount of alloy usage per pour which should yield more boolits per pot of alloy. I needed to reprogram my brain. More perfect boolits per pot is better than just more boolits per pot."
quicksylver
Well-Known Member
Just check my records. I run that mold @ 345, alloy 680.
Alloy consisted of 50% pure,50% lino and 1% petwter.
According to the alloy spread sheet it should give me
a 2.9% tin, 6% antim. and 91.1% lead with a Brinell of 15.
Certainly not a tin rich mixture.
I'm beginning to think too slow a pour.
Or venting issue.
Alloy consisted of 50% pure,50% lino and 1% petwter.
According to the alloy spread sheet it should give me
a 2.9% tin, 6% antim. and 91.1% lead with a Brinell of 15.
Certainly not a tin rich mixture.
I'm beginning to think too slow a pour.
Or venting issue.
OS OK
New Member
Hi fellas, I'm the new guy on the block...thought I'd venture a guess here too.
It looks like the mold is not venting consistently right there, old eyes like mine sometimes need some optical help and better light to see minute lines on the mold face with 'gunk' filling them in. Perhaps a toothpick and a little investigation might reveal the culprit vents.
Another guess...if using a bottom pour you may be ricocheting the pour off one side of the sprue plate hole and cooling the Pb just enough to cause the lack of fill-out.
I dunnoh really...a picture of the two mold faces might reveal something.
It looks like the mold is not venting consistently right there, old eyes like mine sometimes need some optical help and better light to see minute lines on the mold face with 'gunk' filling them in. Perhaps a toothpick and a little investigation might reveal the culprit vents.
Another guess...if using a bottom pour you may be ricocheting the pour off one side of the sprue plate hole and cooling the Pb just enough to cause the lack of fill-out.
I dunnoh really...a picture of the two mold faces might reveal something.
quicksylver
Well-Known Member
Paul ypu might have something there...
I should add that this happens with the 5 molds that I have in 299 ,290 and 284..
RicinYakima
High Steppes of Eastern Washington
In reference to my earlier post, "too much tin" may not be the way to say it. But "too much tin in proportion to the percentage of antimony" might be better.