Testing and Controlling Alloy by Bullet Weight

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  • Last Post 04 November 2023
Wilderness posted this 02 November 2023

I was given recently a block of “lead”, with no idea of what it might really be, other than scavenge. It was probably intended for fishing sinkers before it came my way. Sheet lead? Wheel weights? Battery? Most likely candidate was salvaged sheet lead.

Batteries are of course a no-no for bullet casters. The fishing sinker crowd don’t seem to know about that though.

One reason for testing was to consider the battery possibility.

The test was going to be density. I have a Lyman #32359 mould for my .32-40. With dead soft lead it casts 122.5 gns. If that was the weight I got out of the test material, I’d call it sheet lead. If it was a few grains lighter I’d call it suspicious.

In the event, the bullets came out at 122.5 gns, and were variable quality typical of straight lead. So the lead is a keeper. Now to make it useful.

I was also given by another friend some material that looked like it was cut in ½” strips from a black painted sheet approx. 3/8” thick. My benefactor thought it was solder, and the exposed sides lacked the tarnish I would expect from lead. IF this was solder, a 4% addition to my new lead (looking for about 2% tin) would shift the bullet weight by about a grain.

And yes, the new bullets were 121.6 gns, so I’ll call the other stuff solder. The new alloy casts well and made good bullets, so I kept casting and made the 200 or so I needed.

My point is that with nothing more than a knowledge of expected bullet weights I was able effectively to identify both the gift lead and the purported solder.

In a more general sense, I control my bullet alloys by blending to a previously established weight/alloy – add linotype or hardball to make bullets lighter/harder, or soft scrap to make them heavier/softer.  I am currently using two alloys, based on bullet weights, a soft alloy for subsonics and a much harder alloy for hunting and for LAS Ram loads.

Before I melt a pot of “unknown” I weigh it, and once it is melted I cast 20 or so bullets to get a bullet weight for that metal. If I intend using it straight away, I can then mix in however much is needed of a harder or softer alloy, for which the bullet weight is known, to achieve the desired end weight.

Tin and antimony are of a similar density, and both are less dense than lead.  Bullet weight will therefore give a very good indication of the % of “non-lead” in an alloy.  In the harder alloys, the hardness graphs would suggest that 1% or so each way of tin versus antimony does not make a big difference to hardness. Given that my “hard” addition usually is either linotype (84,12, 4) or hardball (92, 6, 2) the tin:antimony ratio pretty much looks after itself.

When I finish casting I make the leftovers into ingots and label them with the bullet weight. All of this is done with an open pot and dipper.

Edit: The comparative densities i have for lead, tin and antimony are 11.13, 7.26 and 6.68, although I suspect that the values might be slightly different when considering the effect of each on the density of an alloy.

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OU812 posted this 02 November 2023

I have used this method get a rough gustamit on alloy hardness. Do you use a hardness tester? I have the Seco version.

Why can't the pure lead car batteries be used? Couldn't the acid be skimmed or burned off during smelting.

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RicinYakima posted this 02 November 2023

Sorry, there is no "pure lead" in batteries anymore. It is not the sulfuric acid, but the other metals to make the plates harder and more reactive. Even the terminals are not useable lead anymore. 

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Wilderness posted this 02 November 2023

OUB12 - I don't have a hardness tester, and don't feel the need for one now that I have settled into this routine. The weight of the bullets at least does not change over time, and with everything labelled I can produce the required weight on demand.

Re the batteries, the biggest problem is the highly poisonous gasses that can be given off by the dross when it meets moisture. It's about the Calcium and other non-lead components interacting. I'll let others elaborate, but the message is "don't do it".

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John Alexander posted this 02 November 2023

This is an innovative way to estimate hardness.

The question I have is whether there are some different alloys that may have the same density but significantly different hardnesses.

Tin and antimony have about the same density but have much different abilities to harden an alloy. The suggested method depends on the hardness being proportional to density but there is more than one combination of the three components that will have the same density.  

Other metals have the same density for widely different hardness levels.

I don't know if this is a problem for the alloys involved.

John 

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Wilderness posted this 03 November 2023

Thanks John.

Your are of course right, and my reliance on weight as a proxy for hardness depends on the mix being based on maintenance of the lino/hardball tin/antimony ratio, lino being my hardener and hardball being my most usual pickup.

My reference on hardness is the graph of tin versus antimony versus lead in the original E.H.Harrison articles.

From this graph it would seem that the hardness/weight relationship may hold up across a limited substitution of antimony for tin. As an example Lyman #2 (5 & 5) falls between the 16 and 18 BHN curves. Then 10% antimony, no tin, also falls between 16 and 18, as does 8:2 and 6:4. Other combinations are less convenient to the argument.

Away from this area of (my) interest, the hardness tester will be required if comparing alloys of significantly different tin:antimony ratio, though bullet weight will still give a good indication of total "non-lead".

 

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99 Strajght posted this 03 November 2023

I use a method given in Handloader # 50 by Rick Jamison page 18. It uses bullet weight and it works verry well. You have to use a little math and cast a few bullets and use his chart. I use a 405 grain 45-70 bullet but any heavy mold will work. It will even tell you what alloy you have. I have saved myself a lot of trouble with mystery lead. If you can find this old Handloader it is worth it.

Glenn   

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John Alexander posted this 03 November 2023

Wilderness,

Thanks for your very clear reply. Looks like an excellent test used as you are using it.  I would be interesting to run tests with a hardness to see how well it works with unknown ratio's of tin to antimony but might that might not produce anything useful, so maybe not worth the trouble.

Very interesting method.

John

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Eutectic posted this 04 November 2023

 Wilderness

Your method works nicely to roughly determine the % of antimony + tin in usual alloys.

Since the hardness is controlled by the ratio of antimony to tin you need the hardness for full information.

The pencil test is accurate enough for casting purposes and is inexpensive. Search "pencil test" in general discussion.

Knowing the hardness and having enough tin for good casting quality satisfies most casting requirements.

 

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