bullet colorization

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  • Last Post 01 December 2008
sirgknight posted this 13 November 2008

during my casting session this morning I noticed a change in the bullet color.  A lot of the bullets dropped from the mould a very shiny silvery color, but quite a few others dropped out looking a very milky dull color.  The casting session included melting a total of 7 lbs of ingots ( 1/2 lb. each) and occasional fluxing of the lead.  My total bullet count was about 350 with about 25% of them looking milky.  Is this a common thing in the texture of lead?  Is this directly related to temperature?

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RicinYakima posted this 13 November 2008

Since you used the word “texture” I believe that it is “frosting". This is caused by the inside temperature of the cavity being high enough that the crystals of bi-metallic antimony and tin are visible on the outside of the bullet. Even shiny ones have this structure on the inside of the bullets. Most folks don't like this as it is not as pretty as shiny ones. However, I cast all of my match bullets frosted, as this is a excellent way to check for consistency of temperature of the bullets when they were formed.

For plinking bullets, they hold lube better and will be as hard as they can get, air cooled.

Ric

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JetMech posted this 13 November 2008

I think Ric has it right. Sounds like frosting to me also. Some of mine cast better frosted. The thing is, I get that appearance when the temp of the melt is 800 or more. Are you saying that's more a function of the mold temp, Ric?

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RicinYakima posted this 13 November 2008

Dollar Bill,

Yes, it is a factor of mould, inside, temperature and the alloy. 

Alloys that have a wide “pasty” phase are easier to make with frosting. The “pasty” phase is the temperature range from solid to full liquid. WW's, as an example, have a liquid of lead and tin at about 500 degrees with crystals of antimony or antimony/tin and is fully liquid at about 625 degrees. Between these temperatures, there is the pasty phase.

If the surface of the cavity is less than 500 degrees, bullets will be shiny. If the temperature is above that, you will have some degree of frosting.

As the alloy is heated to a higher temperature, the mould gets hotter at a fixed casting rate or cyclic rate. The mould loses heat depending up ambient temperature and air flow. It is easier to get frosted bullets casting is the summer at 90 than in the winter when the shop is at 40 degrees.

I have never been able to frosted bullets with Linotype, because it is eutectic, or goes from liquid to solid at one temperature, i.e. no pasty phase.

I'm not the best at explaining things, but hope that helps.

Ric

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sirgknight posted this 13 November 2008

I've only been in this casting  for a few weeks, but my best guess was that it was a temperature thing.  The bullets seem just fine; in fact, they are some of the best that I have cast.  It's just a color thing.  By the way, once they were lubed, they all looked the same.  They all took on that little dull, lubed look.  Thanks for the info.

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hunterspistol posted this 14 November 2008

You are quite right about that. The mould gets up to full temp and the bullets 'frost' from being poured hot.  Frosted hot bullets aren't really bad, not as bad as too cold(too heavy) bullets. They'll still run a high percentage of bullets the same weight as your best match grade.  Sure, there will be a few light ones but, not so many as to worry about the frost. Hot bullets also have good bases so, they're fairly accurate too.

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jimkim posted this 14 November 2008

I sometimes use a damp sponge or cloth set to the side to cool my mold a little between pours. I read about doing this on another site. Is this a common practice? Is there any reason not to do this?

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JetMech posted this 14 November 2008

That's a good explanation, Ric. If I get it, that means you've done a good job! It's true that I have gotten my best bullets when they are frosted. Good, sharp grooves and bases. The key, I believe as in all loading/shooting is consistency. Keep the  melt at a stable temperature and the mold at the same temp each time you start the pour.

Jim, so you are cooling the mold in between pours. I would guess that you get shiny bullets even if the melt is at higher temps. Like everything else, if you are consistant in technique and get good bullets, I don't see a problem. I would avoid over-cooling aluminum molds to avoid warping the mold, but then I don't have any aluminum molds so don't have any experience to base a judgement on. But the basic technique makes sense to me.

Glenn, are you weighing you bullets? See if you are getting a difference in weight between the frosted and shiny bullets. I doubt you'll get a significant difference it if the melt stays a consistant temp.

Bill

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jimkim posted this 14 November 2008

I don't do it after every bullet. I do it when it “feels” different. If the mold feels different when I open it then I know something has changed and this seems to put things back like they were. I still get frosty bullets. I'm just trying to get “identical” frosty bullets as per Roy's advice. He said it doesn't matter what they look like as long as they are all the same. Rather than run the risk of warping my mould I think I'll just slow down and change the rhythm when I cast. I might play some Glenn Miller when I cast instead of rock an roll.       

 

 

 

 

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hunterspistol posted this 01 December 2008

:armyhelmet: Just happen to think of this.  I use cast iron moulds, so most of the temperature control is in rhythm.  As I've said before, and it's pure Lyman technique, to heat the mould more, I pour then wait a minute before dropping the bullets out, lets the heat exchange places.  The way to cool them is to open the mold for a minute before pouring more(after you drop them).  With the cast iron it doesn't take long to cool the mould when it's open. Heating it up may take several 'pour and hold' sessions to get up to temp. 

Anyway, that's the manual way to do it.

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sirgknight posted this 01 December 2008

Being somewhat concerned about the weight of my cast bullets I invested in an “el-cheapo” electronic jewelry scale.  I weighed about 25-30 150 grain cast bullets and, amazingly,  they either weighed 148.8 or 148.6 grains.  I then weighed about 15 hornady 150 grain factory spire point bullets and they weighed anything between 148.2 and 150.0 and everything in between.  My cast bullets were much more consistent in weight.  It didn't seem to matter whether they were nice shiny ones or milky dull ones.  Thanks for the information.

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