While casting 311299 bullets from a NOE six cavity mold some bullets had frosted spots on the side of the nose. These frosty spots just in front of the lube grooves were a few thousands smaller in diameter. The alloy used was WW with about 2% added tin. They didn't show up every time but often enough to reduce the casting yield. I've not had this kind of defect before. What causes this?
Casting defect
- 5.7K Views
- Last Post 05 October 2012
onondaga
posted this
23 September 2012
You are describing what is termed “zone porosity", it is not related to your alloy selection at all.
Zone porosity is related to the pour technique and is caused by a pouring method repetition that repeatedly has a similar overheating of a particular area of the mold cavity surface. Turbulence of the pour that repeatedly overheats the same areas causes this. The resultant overheated area of the cavity produces a frosted specific area on the bullet where the mold cavity was overheated repeatedly.
The general cure is to tilt the mold about 5 degrees to the left or right and stop pouring directly into the center of the sprue gate holes. Pour on the higher slope side of the funnel shaped sprue gate hole. This is called “Swirl Casting” and sets a circular swirling motion to the metal flowing into the mold..
Swirl casting is not just a cure for zone porosity; it is a very good general casting method for bullet casting because the molds are heated very evenly while casting . Swirl casting also leaves a larger vent in the sprue gate hole while pouring to let air out more efficiently while metal is flowing into the mold with no gurgling. The gurgling of center pouring often sets up hot spots in a mold.
You have to look closer at what you are doing and practice to get really good at swirl casting, but it will get easier as you work at it.
Swirl casting can be done equally well with a bottom pour melting pot or with a ladle, but either takes good hand skill and sharp, observant vision.
I presume you are bottom pouring with a 6 cavity mold. If you are ladle casting you would need a ladle large enough to pour a continuous fine stream to fill all 6 cavities without stopping and have the ladle left at least half full after the pour.
Gary ( retired casting analyst )
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linoww
posted this
23 September 2012
I haven't found casting technique to cure it.Some molds do seem more prone to it though.I never have Linotype do this only WW and i think its due to the arsenic.. Next time it happens I'll try Gary's deal and see if it works.
"if it was easy we'd let women do it" don't tell my wife I said that!
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onondaga
posted this
23 September 2012
"Next time it happens I'll try Gary's deal and see if it works."
Swirl casting is not easy and a big change for the casual or even lifetime bullet caster if you haven't practiced it to a high skill level . None the less, it remains the best manual casting technique and has been for thousands of years historically and in the Archaeological record with precious and heavy metals. It is not just “Gary's deal"
Casting is much more than just pouring into a hole to do it really well under a variety of challenges. It is a science and an art.
Gary
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onondaga
posted this
23 September 2012
"Historically, the most effective method for eliminating zone porosity and voids in casting is the well documented practice of Egyptian Pharaohs beheading the jewelry maker responsible. This lead to many contributions to the science and art of casting.".....from my certified continuing education in Dentistry lecture on sprue reservoir methods versus swirl casting around 1980 when I worked R&D/Education for a major gold refinery.
Gary
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pat i.
posted this
23 September 2012
If I remember right when I had this happen with one particular mold a long time ago (it might have been the Lyman 299) I turned the heat up until the bullet was frosted all over and the problem was solved.
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Pigslayer
posted this
23 September 2012
If I remember right when I had this happen with one particular mold a long time ago (it might have been the Lyman 299) I turned the heat up until the bullet was frosted all over and the problem was solved.
That's wrong!! LOLOL:doooah:
If someone else had of done to me what I did to myself . . . I'd have killed him. Humility is an asset. Heh - heh.
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pat i.
posted this
23 September 2012
I wasn't kidding. That's what happened and that's how I fixed it. Contrary to the latest trend on a particular forum I'm not going to worry about running my pot full of WWs at the lowest temperature possible so I can get shiny bullets or drill holes in my molds to insert thermometers so I can keep the mold at a certain temperature. I cast exclusively with WWs and maybe I'm “Old School” but when I run into problems I turn the heat up and they usually go away. Might not be overly techy or impress the masses with it's brilliance but it always seems to work.
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linoww
posted this
23 September 2012
I'm with pat on this one.I'm too stupid to anal-ize all the variables so i just cast bullets and shoot.Most of the time it works out OK for me.PID controllers-mold thermometers? Not buying into all that.it might matter but the fellows i know who use this stuff dont shoot BR rifles capable of seeing a difference.
George
"if it was easy we'd let women do it" don't tell my wife I said that!
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chboats
posted this
23 September 2012
I have had the same problem especially with the 299 molds, in both Lyman and NOE molds. Like pat i I turned up the heat and it seemed to help. May be it is fixing the symptom and not the problem but it worked. I also found that filling the mold more slowly seemed to help. On a 2 cavity mold I had a lot more trouble with the second cavity filled. It didn't matter which one. I had better results using it as a single cavity mold.
Carl
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onondaga
posted this
23 September 2012
Turning the heat up until all the cavities produce frosted bullets is a remedy that is valid and causes a thermal balance that will, at the least, keep all the bullets in your batch similar looking with a higher level of porosity on the casting surfaces altogether. Surface porosity for many cast bullet shooters is a cosmetic issue only if it doesn't effect group size on the target.
That is not a matter of being right or wrong, it does the job you intended.
That would be a valid solution for the OP,
I believe
The Lyman pressure casting system is pretty relentless at eliminating a number of casting problems but pressure casting still can have the problem of zone porosity with some stubborn molds that will not cast well at all without swirl casting.
Gary
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pat i.
posted this
23 September 2012
Gary don't take offense at this because none is intended but this isn't Cast Boolits. People here don't have to turn pouring piss from a boot into a science project. Most,if not all, problems can be remedied by simple explanations and solutions without all the scientific mumbo jumbo.
I've shot a lot of CBA matches with some really good shooters and if I had started talking about “Zone Porosity” "Surface Porosity” "Turbulence of the pour” "Thermodynamics” they would have slapped me up side the head with a billy club and rushed me to the nearest psych ward! Come on man we're pouring melted discarded wheel weights into a mold you can buy for 20 bucks if it's a Lee. And for the most part the bullets being produced are being shot out of guns that MIGHT do an inch and a half on the best day of it's life if the planets are aligned. PID controllers, mold mounted thermometers, gas check seaters, group buys coming out the ying yang, but never a peep about windflags or bench technique. What's a guy to think.
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Pigslayer
posted this
23 September 2012
I wasn't kidding. That's what happened and that's how I fixed it. Contrary to the latest trend on a particular forum I'm not going to worry about running my pot full of WWs at the lowest temperature possible so I can get shiny bullets or drill holes in my molds to insert thermometers so I can keep the mold at a certain temperature. I cast exclusively with WWs and maybe I'm “Old School” but when I run into problems I turn the heat up and they usually go away. Might not be overly techy or impress the masses with it's brilliance but it always seems to work.
You do make very valid point. Those frosty bullets seem to shoot just as well as the shiney ones! As long as the fillout is good & defined, I'm good to go. Pat, I meant no insult nor ill will in my comment. It's just that when I read your response in reference to the other posts, I busted out laughing. Hope you understand. It's all good Pat.
Pat R.
If someone else had of done to me what I did to myself . . . I'd have killed him. Humility is an asset. Heh - heh.
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pat i.
posted this
23 September 2012
All's good in life Pat and I didn't take what you wrote in a bad way. After I reread what I wrote I can see where it sounded like I was being a wise guy.
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norm
posted this
23 September 2012
I'm with Pat on this one. turning the heat up will cure a lot of mold fill out problems.
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onondaga
posted this
23 September 2012
You guys are a riot. I'm not a fan of the cast boolits site. Actually I'm permanently banned from that site for reporting a vendor and the site owner there for Felony Mail Fraud and complicity to commit Felony Mail Fraud. The case is ongoing and I have been deposed by the court. They probably want to slap me upside the head by now too. More than a handful of members defrauded by the same vendor there have been very helpful to the US Postal Inspector and supportive personally to me in this matter.
Yes, I am one of the science guys about casting but my background in it is most solidly tied to precious metals in Dentistry, but still, casting bullets since age 7 and now 63. I apply the science stuff when I have problems and tend to run with it when someone has a problem and is looking for a reason, an answer and a solution like the OP. Solving casting problems was a big part of my career.
If any of you really get a problem casting, don't hesitate to ask. Just know ahead of time, you might get more than you expected in an answer.
Gary
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Michael K
posted this
24 September 2012
I am happy to see someone else has seen this and has raised the query.
The last batch of slugs that I cast up with my RCBS 24-95-SP and 25-120-SP moulds displayed the same defect. A slightly frosted visual waist just forward or the front driving band on one side. When I first noticed it I thought I had messed up the batch while heat treating. But then further inspection showed the problem in the same place on each of the affected bullets.
I will give both of the above solutions a try. I do swirl my larger BPCR slugs mainly to get a more uniform fill. A larger percentage of my other bullets are usually frosted to some degree. It's likely me, but lower melt temps and my technique(s) result in a higher cull rate then when frosty. My OCD when it comes to cast bullets is limited to fewer culls, narrow weight range (when I do choose to weigh), good fill out with clean sharp corners. Frosty or shiny, I don't care. Can I tell the difference on the targets, nope.
Which of above suggested techniques are right? The one that works for that individual mould.
Many thanks,
Michael.
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pat i.
posted this
24 September 2012
You guys are a riot.
I sure am getting a lot of unintentional laughs in this thread.
My point was that if a certain cast bullet forum was an automotive forum and some guy wrote in saying that his car stopped running while driving to the store their first suggestion would be a valve job, carburetor rebuild, and new rings. My first suggestion would be to look at the gas gauge.
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Pigslayer
posted this
24 September 2012
You guys are a riot. I'm not a fan of the cast boolits site. Actually I'm permanently banned from that site for reporting a vendor and the site owner there for Felony Mail Fraud and complicity to commit Felony Mail Fraud. The case is ongoing and I have been deposed by the court. They probably want to slap me upside the head by now too. More than a handful of members defrauded by the same vendor there have been very helpful to the US Postal Inspector and supportive personally to me in this matter.
Yes, I am one of the science guys about casting but my background in it is most solidly tied to precious metals in Dentistry, but still, casting bullets since age 7 and now 63. I apply the science stuff when I have problems and tend to run with it when someone has a problem and is looking for a reason, an answer and a solution like the OP. Solving casting problems was a big part of my career.
If any of you really get a problem casting, don't hesitate to ask. Just know ahead of time, you might get more than you expected in an answer.
Gary
Am getting a little off topic but I too was permanently banned from castboolits for adamantly complaining about the fraudulent activities of a certain vendor and . . . I too filed a complaint with the USPIS.
Pat, the laughs are all good my friend . . . try and laugh with us.
If someone else had of done to me what I did to myself . . . I'd have killed him. Humility is an asset. Heh - heh.
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pat i.
posted this
24 September 2012
I've noticed before and it seems to be getting worse lately that people have to tread lightly in certain places and don't EVER make a disparaging remark about one of the chosen few or you'll end up on the outside looking in.
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