Casting with Rotometals Lead Free alloy

Ian

Notorious member
Here's my experience based on three pounds of metal and two casting sessions, so there's no way I've mastered this stuff but I did learn a few things which might help the next person.

The alloy in question is the new 87.25Bi/12%Sn/.75%Sb alloy we developed to mitigate brittleness as much as we can figure out at the moment.

First and foremost, this metal does NOT like a hot mould. It flows and fills out pretty well with a room-temperature mould, and the mould temperature I maintained during extended casting (30 minutes or more) was cool enough that I could hold the mould a half inch from my face and just barely feel the warmth. Hot enough to burn skin if touched, but not instant blisters like a 400⁰F mould will. If I had to guess I'd say around 200⁰.

A pot temperature of around 500 to 550⁰ is plenty. My .22 aluminum mould liked 550 but my steel 300-grain .45 mould liked 490.

Another very important thing I learned is just when to cut the sprue. This timing varied greatly between mould block material, mass, number of cavities, caliber, and bullet weight, but regardless is based one one critical factor which is an unique feature of this alloy: Some component (unsure which at this point) that is the last to freeze, takes an unusually long time to do so. If the sprue is cutt too soon, portions of it will smear a tin-like substance across the block faces, and if the bullets are dropped from the mould before this final constituent freezes, the bullets will "sweat" liquid metal from pinholes throughout the surface and be unusable.

Part of the reason the final liquid phase sweats out of the bullet is because the whole structure of the bullet is actually expanding as it cools, unlike our usual lead-based alloy which always shrinks. This expansion of the lead-free alloy upon freezing means that the sprue does not draw in as the bullet cools. It also makes the bullets a little mire difficult to free from the mould blocks, but not prohibitively so; a small rawhide mallet will be your friend.

So the timing of the sprue cut can be determined for each mould by simply watching the sprues as they cool. They will at first be shiny and glass-smooth like pure tin. In a few seconds they will appear to flash over and be solid.....but wait. After they mostly freeze, liquid will begin to sweat out in beads and stay molten for what can be a long time, from 30 seconds up to several minutes depending on how quickly the heat of the poured metal is dissipating. What I found best is to cut the sprues just as the little sweat beads become firm, but not completely solid. Cutting the sprues worked best for me to do with a gloved hand, but takes some effort. Deliberately forcing the sprue plate against the block faces as I cut them helps form a good bullet base with no nib and minimizes tear-out. If you cut the sprue too late, it simply breaks out a little crater; no big deal if it isn't too big, but there is a sweet spot to try and find fhat will give perfect bullet bases.

I found that filling the sprue well and forming a "blob" is all that is necessary. If too little sprue is poured, the bases can become rounded. Any more sprue volume than necessary only adds unwanted heat and extends the cooling time.

Freshly poured:

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After the first "flash over", the sprue becomes very hard, but it isn't ready to cut yet:

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Now the sweat beads have formed, and after a much longer interval of time have set up:

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Better picture from a different mould:

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Ian

Notorious member
After the sweat beads have firmed up, the time and temperature are correct in my estimation and this is what you get:

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This sprue-cooling phase would take anywhere from 20 seconds with a four-cavity aluminum .22 mould to three minutes with a two-cavity, steel .45 caliber. The Lee 358-200RF two-cavity would take exactly two minutes for the sprue to cool sufficiently to not smear and not ooze out metal after the bullet was dropped.

I also cast some hollow-point bullets this last session, employing the "Mould from Hell" as a sort of worst-case scenario with regard to the expanding alloy being difficult to free from the blocks and the long, HP spuds wanting to hang on to the bullets. The brass MP 30-silhoutte mould did fine although a lot of tapping with the mallet was required and I had to pull almost all of the castings free from the pins with pliers. Since loss of heat necessitating fast cycle rates is not so much of a factor with this alloy as it is with lead, I had plenty of time to piddle with removing the bullets from the mould. The HP cavities were well-formed even with cold pins, so that's another plus.

That's pretty much all there is to it, I'll leave the last post as a quick-start guide and include some comments on the nature of bullets cast with this metal.
 
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Ian

Notorious member
QUICK START GUIDE

  1. Begin with a clean, uncontaminated furnace and tools to ensure no lead traces make it into the lead-free bullets. Traces of lead on bullet moulds should be removed.
  2. Heat the alloy to about 500⁰F, flux and skim as you normally would with a lead alloy.
  3. Warm the mould slightly by placing it atop the melting furnace, or simply start casting with it. Every one of the six moulds I have cast this alloy with so far warmed up to equilibrium temperature by 10-15 pours.
  4. Begin filling the cavities, pouring as much sprue metal as the well will hold without spreading too much across the plate.
  5. Watch the sprues for the initial dulling as they freeze and wait for beads of metal to ooze out and firm up before cutting.
  6. Cut the sprues with a gloved hand. I like to place the mould sprue side down in my right palm and shear the sprues off by pulling the plate with my fingers while pushing against the block with my thumb. Since the mould doesn't need to be so hot to cast this metal, a better grasp of the mould and sprue plate is possible than normal without setting uour hand on fire...and that extra grip is needed because the sprues are about as tough as fully-cooled pure lead.
  7. After observing the bullet bases and making certain that no liquid is oozing out from the sprue cut, tap the handle pivot bolt smartly with a mallet to crack things loose and open the mould. Tap the hinge bolt again until the bullets fall free.
  8. Close the mould and refill immediately.
  9. Take note of the time it takes for the sprue to be ready to cut, and once the mould is warmed up and that time normalizes over several pours, your mould is at equilibrium temperature and you can judge future cooling times by the clock rather than poking at the sprue every few seconds.
Some further observations.
The bullets will be very hard when they fall from the blocks and not much care is needed to keep from damaging them.
A sprue plate lube isn't necessary but doesn't hurt as long as you don't use too much. Remember that this alloy requires very little heat in the mould to cast well, and the bullet is pretty close to its final hardness when the sprue is cut.
Clean cavities work best, smoke isn't necessary.
While every mould material is unique, I haven't found a material preference yet, so run what ya got.
Moulds I cast with: 4C Al NOE 22-67FN, 2C Lee C309-160RN, 2C steel AM 45-297G, Lee C358-200RF, 3C MP Brass 30 Sil HP, 1C Lyman 452374 Devastator HP.
Deep, square lube grooves are a little more difficult to cast, but not too bad. I haven't found a mould yet that wouldn't work just fine with this alloy after its particular time, temperature, and tapping preferences were established.
The bullets will cast .002 to .004" larger than normal depending on caliber, factor that in to your mould selection.
Gas check shanks will be large, so plan accordingly. Tapered shanks are the worst because the lead-free alloy doesn't swage easily. Thinner, homemade aluminum or copper gas checks may be a requirement for some moulds.
The lead free alloy doesn't spring back quite like lead alloy does, so the bullets may come out of a sizing die smaller than usual.
If sizing more than .002", lubricate the bullets. I roll them on a case lube pad but there are many ways.
If using a base-first bullet sizer, plan on not sizing more than .001" or things can break. I size in push-through dies first and finish in the luber-sizer.


Below are the results from my second casting session. The 452374 HP bullets are wrinkled and rounded at the lube groove because Ibused that mould to empty the pot and alloy was cooling off and not filling the mould fast enough.
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Results of the very first casting session and some smash tests.
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NOE 22-67FN after sizing nose-first in a form die.
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What happens when you don't let the bullets cool enough before cutting the sprue and shucking from the blocks.
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Ian

Notorious member
I'm considering it. They cast about .315" and don't much care for Hornady gas checks but it could still happen. I'm a little curious if they will survive the slamnification an LR-308 will give them. Also curious about the obvious 'splody tip. The .45 ACP bullets will probably get loaded next, just for the hell of it.
 

fiver

Well-Known Member
well there is this place called California that won't allow you to use lead alloy in the field.
this is the work around.
 

CZ93X62

Official forum enigma
CA does have unicorns and rainbows, though. There ARE compensations. :cool:

Louie--Barnes Bullets does a fair job of supplying common calibers with usable hunting bullets. Cranks Like Me insist upon hunting with prehistoric calibers like 25/20 WCF, 32/20 WCF, 38/55, and 44/40 WCF that Barnes likely will not get around to servicing. This process fills a niche--albeit expensively--that will allow Cranks to keep old rifles and handguns hunting.
 

JonB

Halcyon member
>>Just in case anyone plans on hunting with this alloy in California.

I copied most of the following from another poster on the other site, as I found it interesting. I guess I just like to know what laws other states have on the books, and the details to follow them, especially the laws that the State of Minnesota is considering.
...btw, the first link to a certified list of ammunition, includes RotoMetals.
--------------------------------------------------------------------------------------------------------------

California certified nonlead ammo​

California allows only nonlead ammo which has been submitted and certified.

From CDFW website:
"Where can I find a list of nonlead ammunition legal for hunting?

CDFW and the California Fish and Game Commission have developed a process to certify projectiles as meeting the nonlead threshold (less than or equal to 1 percent lead content) for purposes of these regulations. A continuously updated list of certified nonlead ammunition for hunting is available on the CDFW website.

Manufacturers are required to undergo an application process to have their ammunition certified as legal for use. Information regarding the certification process is also available on the CDFW website."


Here's the link to the certified list:

If a warden suspects non-certified lead-bearing ammo is in possession while hunting, they may seize it for lab analysis:
How will wildlife officers check for compliance?
"All ammunition in a hunter’s possession may be inspected by wildlife officers. In some cases, if a wildlife officer suspects a hunter is in possession of lead ammunition and cannot prove otherwise in the field, he or she may seize a cartridge or bullet for further analysis. Hunters are encouraged to assist in confirming compliance by retaining and carrying in the field ammunition boxes or other packaging."

Exception is made for pellet rifles to use lead ammo, as they are not firearms.


edit: you can apply for certification as a private party, but the warden with whom I spoke awhile back said he did not know of any private party being approved.

here's the application link:

 
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richhodg66

Active Member
Interested to hear how they shoot. Hopefully we can eventually get some expansion tests.

How much does this alloy cost?
 

Ian

Notorious member
Rich, I had another thread on how they shoot, even killed a little spike buck with my .223 during a range session. Bottom line is they shoot as well or better than lead-alloy bullets.

The alloy is very expensive, but for hunting, $50 worth will go a long way.
 

RicinYakima

High Steppes of Eastern Washington
I tried writing an article from Ian's work last year, but it never went anywhere. Other than scientific curiosity, there just aren't enough people interested in non-lead cast bullets.
 

richhodg66

Active Member
I coach a high school air rifle team, have for about nine years now. About five years ago, we were mandated to stop using lead pellets. Tried a few different ones before settling on the ones the CMP recommended.

I took three different types we had tried and sent them to someone who has the equipment to test alloy content. All three were, for all intents and purposes, pure tin. There were trace elements that amounted to well under 1%, nickel in one, copper in another, can't really recall. The pellets we use now are very good. I'm sure with very high end rifles and very good shooters, one might see an accuracy difference between these and lead, but so far I haven't had a shooter good enough to make me feel it would make any difference to be using lead.
 

Rockydoc

Well-Known Member
Ian, you live in Texas, do you hunt in California? Or this an academic exercise?
I find this very interesting although I will likely never cast any of this metal.