Chipped edges

[fatelk]

I'm having a little trouble with tiny chipped edges on some bullets on the leading edge of the front band, as they come out of the mold. I've seen this problem before in the past but don't remember how I prevented it or even if I did. I'm sure it's been addressed here before but I couldn't find anything in a search.

It's a nice little single cavity 429244 that I've used before and gotten good bullets. The lead is an un-scientific mix of range scrap, WW, and a little linotype. The temperature is around 700°F. I wait a few seconds for the sprue to harden, and the sprue plate cuts very easily but no smearing. The bullets drop pretty easily from the mold. Some need a little tap.

Mold problem? Alloy problem? Temp problem? Mold too hot? I've cast a lot of boolits, but it seems that the more I learn, the less I know!

Thanks all!

[Duckdog]

I've also run into this once before and it boiled down to allowing the mold to cool just a tad before cutting the sprue. I do believe it is an alloy issue as well. It did not affect the way the boolit shot, if I remember correctly. I'm also waiting to see what comes of this!

[runfiverun]

count a little longer and turn the alloy down some.

[prs]

More time for the alloy to solidify in the mold. Its OK to cut the sprue so long as the cutter is not smearing lead onto the block tops, but give it a bit more time before opening the blocks. If such time taxes your pace, you can cool the blocks occasionally upon a damp rag or upon a good sized metal surface acting as a heat sink.

prs

[Larry Gibson]

"The lead is an un-scientific mix of range scrap, WW, and a little linotype."

An over abundance of antimony in the alloy is the problem and not enough tin. Most range scrap has a high % of antimony anyway. So does COWWs and linotype certainly does. The antimony level of your alloy is well above the saturation level at which it will mix into solution in lead. Even with the small amount of tin in those alloys there is not enough the form SbSn to go into solution and stay there in the lead. The excess antimony hardens before the lead does and separates out, most often in the outer edges of the cavity where the mould cools first. What is chipping off is such antimony. Many think that adding linotype "sweetens" the RL or WW alloy by adding tin. It doesn't. What tin is in linotype is already combined with the antimony there as SbSn and won't combine with the excess antimony in the WWs or the RL.

I suggest adding lead at 3-1 (RL - lead) and adding 2% tin. Save the WWs and linotype to make #2 Alloy.

Larry Gibson

[sealer]

let the mold cool just a little longer
dennis

[fatelk]

Thanks everyone. Letting it cool just a couple seconds longer did the trick. I was hoping it was something simple like that. That little mold makes good bullets, but one at a time sure is SLOW. That's OK though, because I don't shoot a lot of full power magnums through the Marlin 1894, and that's what this is for. A couple hundred bullets will last a long time.

I bumped the temp down a little as well, found that about 355°C was about right (670°F - my controller only reads in Celcius). much cooler and fill-out didn't look right.

Thanks, Larry, for the metallurgy info. I wrote down your suggestion on paper and will put it out by my casting area to try on the next batch. I've got a pretty good supply of pure lead (for black powder, which I shoot very little of), and about ten pounds of solder which should go a long ways.

Thanks again guys. You all are great!

[leadman]

You may want to inspect the mold also for a small sliver of lead stuck to the mold in that area. I have a Lyman SWC mold that does the same thing sometimes.

[lwknight]

The leading band is not related to when you cut the spru but rather casting cadence in general.
Letting the mold cool a bit longer will indirectly help you by lowering the actual mold temperature because you will be casting slower.
Alloys with a good tin content don't like molds too hot.

[prs]

Several of us gave the easy answer of letting it cool (yours truly guilty, as charged). Larry G. gave the correct inside dope on why such alloy needs the extra time. You will not see that problem with pure lead or chiefly binary lead/tin blends. Blends with balanced tin and antimony plus the lead base will also be malleable and resist the brittleness when hot. So your long term goal will be to render your scrap into a more balanced tin:antimony blend were you have at least 1% SN and preferably 2% SN to allow excellent detail in your finished product and to keep SB at or close to the tin content. Antimony is probably going to be there a bit in excess, but adding tin to balance is expensive. Thus adding known or "suspected" pure lead lets you dilute the antimony and save the tin, so long as the end result regarding hardness suits your application. In the short term, with the alloy as you have or had it, those boolits may give you what you see to be leading, but don't be surprised if the "leading" cleans easily from the barrel. That is because it is mostly antimonial wash, a grey smear coating from the outer skin of your boolits. That is not much more difficult to remove than primer or powder residue. For subsonic pistol rounds, I tend to use a blend that is about half or even less of Lyman 2 by weight percentages.

prs

[1_Ogre]

One way I avoid this is by always casting more than one boolit or caliber at a time. Load one mould, set it down and load the next, go back to the first and knock off the sprue, etc, etc, etc. This way my moulds have enough time to allow proper cooling and I eliminate the chipping of the front edge of the boolist. Just my opinion and the way I cast.

[MT Chambers]

X2 Brittle, add tin.