Rotometal lead.

[Gunlaker]

I used to buy 99.99% lead from a local place. They also sell ingots with 2% antimony. I don't know if I got one of the 2% ingots mixed in (they are 60lb ingots and I was buying them 5 or 6 at a time), but I had a bunch of bullets that were, if I remember correctly, about 8 grains light. I could tell as soon as I started casting, the melt temp was just a bit lower, and it was really hard to get perfect bases as the sprue would tear just a little. The bullets did shoot very well though.

I heard good things about Rotometals so switched a while back. So far I haven't had any significant changes in weight from batch to batch. I like to buy 150 lbs at a time so I have as little variance as I can get. I will be on the lookout for it though.

Chris.

[Kurt]

Thank you Robert.
This is good information to know.

The alloy I had mixed is all used. It will work fine using a little thicker paper then I usually patch. My Stevens action will cam a one thousand over bore with out a problem. I shot 10 today, the temp broke the 50 degree line and the 10 rounds where tight round group so I don't think it will be a problem.

The new bullets are few grains lighter weight bullets compared to last years alloy made me dig into this. The thumb nail test also had a shallow scratch compared to the last years leftover bullets.
The plus side to this is if arsenic is in the mix the bullets will keep their shine and not turn gray.
I made a comparison hardness test using a Lee tester and there is a difference between last year and the new. The old alloy has a .080" imprint and the new has a .078" Both have 16# lead 1# tin.
All is well........Kurt

snip.......
Have any of you that just got a new supply of lead noticed any weight change or hardness ?? These pigs where listed as 99.9% pure. It sure does not show this from the recovered bullets. I wonder if they reclaimed a bunch of lead shot that has antimony in it and called it 99.9% snip...

Kurt and all, attached is a note written to friends that cast. Is it possible the supposed "pure" metals can have trace elements. It may help to compare as cast diameter of new mix with your known alloy. Also just squeezing one bullet cast of new VS one of known alloy crossed in vice will 1) show hardness comparison 2) show any micro cracks hinting of Arsenic presents. Hope this helps

One item that has surfaced is topic of casting Alloys and varying amount of hardening mixtures. I lifted the following from an issue of American Rifleman that is so old the print copy has 98 pages. A key component in hardening alloys is with Antimony. One of the sources for Antimony is Shotgun pellets. Particularly the Lawrence brand of magnum shot contains higher antimony that may be blended in our casting pots. CAUTION however is noted because along with Antimony the shot alloy also may contain Arsenic. The Arsenic is used in shot manufacture as it effects the surface tension of molten alloy. The positive effect of arsenic causes the droplets of metal to form more perfect spheres while falling through air. Arsenic in vary trace amounts assists Antimony in hardening the cast pieces. On the negative side, strings of high Arsenic result in cracking. Micro cracks are caused by shrinkage porosity in bullets cast entirely of lead shot. Arsenic is of course hazardous to health. These facts and more here are attributed to Col. Harrison’s published books. “Arsenic is also a benefit in cast bullets where it improves the hardness of antimonial alloys, and optimum concentration range for arsenic of 0.1 to 0.15%.” “At these levels arsenic increases the as cast hardness of most antimonial leads and it also provides the capability to heat treat alloys like wheel weight metal to 30BHN or more.”
I’m not sure of the need for harder alloys in our BPCR loads especially if one expects the bullets to expand to help seal the bore. However, the following might help our understanding of what alloy components will do to as-cast mold diameters. “A little-known fact about elemental Arsenic is that it contracts 10% on solidification compared to 3.4% for lead, 2.8% for TIN and 0.8% for antimony”.
There were ample cautions about melting lead shot. The presents of Arsenic adds smell of Garlic and is of course determinantal to health. Adding shot in small amounts may best be taken on OUTSIDE in open air. Once melted in low concentration the normal exhaust precautions should be followed and work.
Setting the alloy with Arsenic aside my eye caught the fact that Antimonial alloys shrink LESS on solidification. Therefore, if we wish to cast bullets that are maximum for mold diameter the alloy should contain amounts of Antimony. Unfortunately melting of pure Antimony is tough due to its higher melting point. Casting hard alloy bullets may be unproductive unless as-cast diameter is properly greater than bore I.D. Casting hard alloys requires more detail to bullet to bore fit. They also require higher forces to put through lube dies. I’m not sure any of you will find these details of value. The “discovery” is worth sharing if not only as background for our casting ops.

best regards RobertB