Bullets look bad on one side

  • Last Post 29 December 2011
hanovergray posted this 12 October 2010

I am trying to cast some 45-90 bullets for my bpcr rifle. I have cast bullets for about 18 years but just started with bpcr. The problem I am having is on one side on the nose of the bullet keeps coming out frosted. I am using a lyman mag 20 and I use a ladle with 20-1 lead. After three casting sessions trying everything I could think of I switched moulds but had the same problem.I have attached pictures so you can see what I am talking about. Any help would be greatly appreciated!

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hepburn45110 posted this 12 October 2010

I have a mould that does this very thing.  The problem seems to go away about 200 bullets into a casting session.

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RicinYakima posted this 13 October 2010

There are two things that I have had happen that cause this:

One is residual oil left in the side of the one mould block. If washed and dried well with Dawn dish soap, it seems to help get the oil out of the pours of the metal.

Or contaimination of tin and lead oxides that are coming in from the ladle. It might help to clean the ladle so that it is bright metal. It sticks to the side of the mould that is on the bottom when ladel pouring.

HTH, Ric

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hanovergray posted this 14 October 2010

Thanks for the ideas I have received. The next chance I get I will try them.

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onondaga posted this 09 November 2011

The question is an old one and I have an old answer.  I am a retired casting analyst and what you are showing is “zone porosity". This is associated with either a hot spot or a cold spot in the mold usually related to casting technique when it presents frequently in a particular mold, usually a heavy one.

You are likely very consistent in your pour method and usually get great results. Some moulds just don't behave with the usual method and you will have to modify your pour to stop the problem. The metal gets the most porosity at the last place that it cools, that is just physics.

I suspect you are creating a hot spot in your mold by a consistent pour method that is overheating a spot in the cavity.

The classic cure for a hot spot causing zone porosity is to try swirl casting. Control the flow of your pour with the mold tipped about 5 degrees and direct the flow 1/2 of its diameter off center into the sprue gate's high side slope into the hole. This will leave room for air to escape easily during the pour and set up a swirling flow of metal into the cavity that will heat the mold evenly every time.

Practice that and learn to do it well and the zone porosity will disappear. It is not an easy skill to develop with a ladle but it can be done. It is much easier with a bottom pour spout.  The Lyman pressure casting method may also work if your mold design will tolerate that, but swirl casting is usually the better cure.


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.22-10-45 posted this 22 December 2011

Hello, onondaga. “swirl casting” that is the best advice concerning bullet casting I have heard in a long time! Ever since day 1 of bullet casting, I have a solvent to clean moulds..carb. first carb cleaner..until they started adding lube, than to brake cleaner. during the last few casting sessions, I was having trouble with mould fill-out in only one cavity..always the block with sprue cutter..I even went to scrubbing with hot detergent & toothbrush..something I had never done before..but I like the results so much, I think it will be my std. practice from now on. However..even this didn't take care of problem..I was going nuts trying to figure this out..until I tried altering dipper angle to sprue hole. This seemed to take care of the problem. The funny thing is, I had never experienced this problem with this very easy to use mould in the more than 30 years I have had it, (Lyman dbl. cavity 375248). I might try giving the ladel a good INSIDE cleaning & mould-prep treatment too. In both moulds, defect was limited to block with prue cutter..more metal mass must allow this hot-spot?

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onondaga posted this 23 December 2011

.22-10-45: Hello!

Determining exactly what is causing a hot spot is very difficult. Fortunately the results of a hot spot are easy to see and identify. Repeated porosity in a localized area of the casting is a sure sign identifying a hot spot. So, what ever is causing it, when you develop the problem, try the swirl casting method.

I only clean my bullet molds with hot soapy water except when I have a new mold that is not releasing bullets well. Then I use Comet and a brush or the last resort of casting a bullet with a hex nut over the mold hole instead of the sprue plate. This makes a honing tool that can be rotated with a wrench and I use comet or 500 grit pumice mixed with dishwashing liquid for a polishing paste in the mold.

A lot of casters have their favorite mold lubes and lubing method that work fine for them. I will only recommend that no petroleum or petroleum distillates be used at all. I use a Silicone grease like automotive clear silicone dielectric grease. I apply it to the sprue hinge screw and collar and to the mold locating pins or ridges and slots .


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corerf posted this 24 December 2011

Single cav or double?

If its double, I have the culprit.

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billglaze posted this 25 December 2011

This may sound weird, but I've had the same problem with two double-cavity moulds, but my situation may be different. I remember when years ago, Lyman started blueing the inside of their moulds to cut down on break-in time. Worked pretty good, too. I have had some moulds that the second loading of the mould yielded perfect bullets. But, in these other cases, (well used moulds) I noticed a slight discoloration of the mould side that was giving imperfect bullets. Sometimes it took up to 2oo castings to get mostly good bullets. It acted as if this one area wasn't getting hot enough. Not acceptable. One day, I noticed the mould in question had a different color on one side. It wasn't blue, but kind of tawny. I had a bottle of home blueing on the shelf, and, thinking “Why Not?” I re-blued the mould half just to see what would happen. Worked perfectly! I've been using this mould for thousands of bullets ever since. I've done this on 2 different moulds, (Lyman, RCBS) with the same results. However, I realize that YMMV, so all I can say is that it worked for me.

In theory, there's no difference between theory and practice. In practice, there is. My fate is not entirely in Gods hands, if I have a weapon in mine.

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Ken Campbell Iowa posted this 27 December 2011

i wonder just how bad a problem such an off center frosted blemish might be.....   would be very interesting to try several groups comparing the blems with non-blems. i am thinking such a small variation in symmetry would be insignificant relative to all the other nasty things that can happen when we launch one of our semi solid slugs.

ken in the sticks

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CB posted this 29 December 2011

I am with Ken. Does anybody know if this hurts accuracy. If not why not find out and maybe ignore the cosmetics until they go away.

Us cast bullet folks spend a lot of time fixing what ain't broke and often little time testing to see if it is broke. I think that is backward.

John -- also in the sticks

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onondaga posted this 29 December 2011

Overall frosted or satiny appearance is fine with me.  A pocked and pitted appearance is not OK with me.

The satiny look holds my 45:45:10 Recluse tumble lube better, that is one positive point about mild overall surface porosity.

Bullet mold temperature, casting cadence and alloy temperature will all effect the surface appearance of cast bullets. A skilled bullet caster can even manipulate those variables to control “as cast” bullet diameter with a swing of as much as .002” in some bullet molds. Try yourself and measure some “cold” mirror shiny bullets diameter against overall satiny bullets...Use a real Starrett mike with a gentile touch and not a dial caliper and you will see the difference in hand.

The zone porosity of the original poster here does not appear to be a serious one with major craters that would throw bullet weight way off or distort bullet seal, but more of an aesthetic grief. None the less, zone porosity is correctable with swirl casting discussed above.


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