Large weight variation when casting pure lead?

[Sturmcrow]

I have been casting for a little over a month now. When casting wheel weights into 300gr Lee .452 bullets, I get a standard deviation of 0.7grs. I cast some pure lead today, and the standard deviation of 65 bullets was 3.5grs. All of the bullets were cast from the same melt.

Is it normal to have such a high SD with pure Pb? I think that part of it was melt or mold temperature, as the lighter ones were wrinkled. I know that tin is supposed to allow better mold fill-out. Is this my problem?

I am casting pure lead because I want to use these as cores for "swaged jacketed bullets in .40 S&W or 45 ACP jackets." Ultimately, these will be used in .454 Casull rounds.

[Calamity Jake]

Your having fillout issues with the pure, add 1-2% tin and try again.

[GabbyM]

Pure lead likes more heat than an alloy metal.

[stubshaft]

You really have to pour on the heat when casting with pure. It has a higher melting point than most of the alloying components.

[SlippShodd]

What stub and Gabby said... pure lead is a beach to fill mould blocks with. I know, it sounds counterintuitive, but just up the heat of the melt (my lyman casting thermometer says something like 600-700*, I've had to go to 750-800 at times) and get the mould really hot as well. Then don't let it cool, don't stop to admire them. When you're consistently dropping boolits with sharp edges, the consistency in weight will be closer.

mike

[Sturmcrow]

Am I correct in assuming that the main reasons not to cast hot with alloys are not important for pure lead? Mainly I thought we should cast at a minimum temp to keep from preferentially oxidizing the alloying materials. Without those other materials, is there any problem with casting pure lead with my Lee melter going at full blast?

[Sturmcrow]

I cast a couple dozen pure lead today with the melter going full blast and the mold very hot. In the past, my discard cutoff has been plus or minus 0.5%. At that rate, more than half were culls from the ones I cast yesterday. Today, all of them were within 0.1%. That is pretty darn accurate casting, if you ask me.

Thanks for the advice. I did not add any tin, but bumping up the temperature appears to have helped me out. I also cast a few 0.365" round balls today and they too came out very close to one another.

[Sturmcrow]

On a related note, how much does temperature affect casting weight variation when you do have enough tin? I've been using an IR thermometer, which I realize is not very accurate. Is it worth it for me to invest in a real casting thermometer? Any suggestions?

[runfiverun]

mold temp is the key.
a 40 S&W case won't take a boolit too big, i use a 358 180 gr boolit as my cores in the 40 case to make 44 bullets from. they are 180+70=250 grs give or take depending on the case.
rem and speer are the bigger interiors followed by federal then winchester.
cbc, ivi, are between federal and remington. and cci is closer to winchester.
i have used 375 cal 240 gr boolits to make 315 gr bullets from the 40 case.
and some 280's to make 350's.

[fredj338]

On a related note, how much does temperature affect casting weight variation when you do have enough tin? I've been using an IR thermometer, which I realize is not very accurate. Is it worth it for me to invest in a real casting thermometer? Any suggestions?

Hotter will shrink a bit mroe so you'll see more variation, bigger bullets show more weight variation than small bullets. With a 300gr, +/- 3gr is still fine.