Need advice on figuring out alloy mixture for making cast bullets

[johnnymoff]

Hi,

I want to start casting my own bullets and want to understand what to shoot for in terms of BHN and what alloy mixture gets me there. I am looking to cast 9mm Luger 115gr for simple paper punching.

My plan is to start by casting a pre-mixed alloy and then later on start sourcing pure metals and mix myself. This should make things a little easier for me until I am comfortable starting from scrap.

My specific questions are:
1. What is the BHN or range of BHN appropriate for what I am trying to make?
2. Do I need to pick an alloy with all three metals: lead, tin, and antimony?
3. Which one of these alloys is best for what I am trying to make: https://www.rotometals.com/bullet-casting-alloys/

I think I can figure out #3 based on the answers to #1 and #2 and the formula on the rotometals site: Brinell = 8.60 + ( 0.29 * Tin ) + ( 0.92 * Antimony ) but would still welcome your thoughts.

Thanks
-John

[RogerDat]

I think you could probably get away with a mix of 50/50 Lyman #2 alloy and plain. Would be 2.5/2.5/95 alloy BHN ~11.6 should work if you are buying the alloy from Rotometals. One ingot of each per 10# pot.

Or you could go to the forum swapping and selling, check in the vendors and buy some COWW (clip on wheel weight) lead for around $1 per pound. Then purchase some pewter or tin sufficient to add between 1% and 2% tin to the mix and that would probably work fine. For a lower cost.

That said it can certainly remove some uncertainty to purchase foundry known alloy. Allowing you to focus on casting until you feel you have that down. Then move onto making your own alloys.

antimony makes lead harder, tin helps molten lead flow better and while it also makes it harder tin takes a lot higher percentage to gain much hardness. Tin also helps make lead more malleable. That is bend more without breaking. There is also an alloy that forms between tin and antimony that can change the characteristics of the lead, balanced the two ingredients have more impact than on their own.

Some revolver and slower velocity rifle is made with just tin and lead. Cowboy action shooting competition I think is limited to those two metals since back in the olden days that was all they used. Muzzle loaders use plain soft lead, no antimony, no tin. So no you don't have to use all three. But the three can work really well together. Copper in tiny amounts will alloy with tin and can be added to the melt. That makes a bullet tougher, unlikely to break up on impact or less likely deform from firing at higher velocities.

You have a lot of interesting reading ahead of you, so until you learn a bit more about the alloys nothing wrong with buying them from a foundry, cost more for purity and convenience is all.

[johnnymoff]

Thanks for the quick reply, RogerDat!

Would just using Lyman #2 work too? I think that would get me a BHN of ~14.7 based on the formula or maybe a little higher like 16 based their description of the product.
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I can order the nuggets and experiment with mixtures ranging from ~11.6 to ~16. I am assuming that the nuggets are no different from the ingots with respect to making mixtures.

Thanks,
-John

[TexasGrunt]

How are you planning on lubing? Hi-Tek or PC will allow you to use a softer alloy. I use 50/50 COWW/Pure with 2% Tin added for all my pistol boolots. That's 9mm, .38/.357 10mm, .44 Mag, and .45 ACP. I use both Hi-Tek and PC and have no problems.

Elmer Keith thought 1:20 was hard lead. That's one part Tin to twenty parts Lead.

[johnnymoff]

Semper Fi to you too!

I was going to ask about lube later and so have not thought about it yet. What do you use?

-John

[David2011]

All good answers so far, assuming you're not loading for a Glock. I would go with Hardball if going with RotoMetals alloys since you're specifically asking about 9mm. IMO Lyman #2 wastes tin since you get good wetting and flow at 2%. Tin is expensive so it ups the cost unnecessarily. I've found clip on wheel weights plus an additional 1.5-2% tin to be adequate for 9mm. Actually that's a good alloy for about any mid range handgun boolit. The .45 Colt/ACP cartridges are low pressure, 9mm/.40 are at the upper end of non-magnum cartridges. I just don't shoot a lot of high pressure loads, mostly some .44 mag from a Contender (very stiff loads) and some "Ruger only" .45 Colt for dispatching wounded feral hogs so defer you to those with more experience in that area.

[Bigslug]

I would probably second Hardball as a choice for a starting mix, though the extra tin of #2 might help with mold fillout while you learn the casting game, it is a bit pricier.

These are both fairly hard alloys for pistol (16 and 15 BHN, respectively), but as you will learn through more reading, 9mm brass can be a tricky bugger with a tendency to size bullets down below desired diameter on seating, causing barrel leading. A harder bullet of correct diameter is one solution. My father's added solution was to swipe the Lee sizing die for my .38 S&W set (slightly larger expander) to minimize this effect.

[runfiverun]

the 9's I have seem to do just fine sized to 358.
an alloy similar to 1% Tin and 3% antimony is just about right for target type loads.
I drop it in water from the mold and use it in my rifles.
if I needed harder for a hand gun I'd drop them in the water too.

lube is the easy part.
I been doing an experiment starting at waay too wet and working towards dryer and dryer mixes.
they have all shot well except the waay to wet mix.