high antimony alloy: how fast can I push it?

Standard Member

454PB posted this 24 November 2009

If you're willing to take some extra steps, water quenching or heat treating will stretch out your supply of type metals/high antimony alloys.

For instance, I mix pure lead 2 parts, 1 part Linotype and then drop them in cold water from the mould. Size them quickly, since they begin to harden within hours. End result is BHN 20 to 22 and they aren't as brittle as straight type metal.

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Standard Member

Nuggets posted this 24 November 2009

Bullet's http://en.wikipedia.org/wiki/Brinell_hardness_test>BHN x 1422 = http://en.wikipedia.org/wiki/Pounds_per_square_inch>Pounds per square inch

http://en.wikipedia.org/wiki/Obturate#cite_note-1> http://en.wikipedia.org/wiki/Obturate>http://en.wikipedia.org/wiki/Obturate

Have a look at this web it may shed a little more light on the question. Regards. Nuggets http://en.wikipedia.org/wiki/Obturate#cite_note-1>

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biddulph posted this 24 November 2009

Hi Dicko,

thanks for all that info. I don't plan to hunt with cast at this time and know how to make up Lymans # 2 if I do. I'v got lots of jacketed hunting bullets, bought at a time before I started using cast exclusively at the range.

I need to get a chronograph, its on my wish list, and dont worry about teaching grandmother to suck eggs, all info is useful, to me and, I am sure, to others that read the thread.

I made up some lino type alloy and cast 265 gr .375 bullets which I fired with 13gr Red dot with much poorer results than I got with same load but wheel weights. I gues its lack of obturition (spelling?). Groups at 50 yards went from ragged hole to 2". Will try again with plain lead bullets and see what I get. Lots of variables in this game!

Would love to buy a copy of your book when it comes out!

cheers

James

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Standard Member

Dicko posted this 23 November 2009

Hi Bidulph,

You are right, what you have is harder than linotype. What's not generally known is that there are many “standard” lead/tin/antimony alloys. Standard, that is, for specific purposes. So you have linotype, monotype, foundry type, Lanston standard and others. What we think of as linotype is 4% tin 12% antimony and is 22 BHN. Pure lead is 5 BHN. I'd guess that the stuff you have is about 25 BHN. As linotype casts very well your stuff should too. Should shoot well too, and 25 BHN is only one quarter the hardness of jacketed bullets. So I'd be inclined to cast as is. Just be aware that the higher the antimony content the more brittle the alloy, and it becomes quite frangible.

Don't use it if you plan to hunt roos, you won't get humane kills, you might well get nasty surface wounds and condemn the animal to a slow death from infection. The rule of thumb for cast hunting bullets is Lyman # 2 alloy which is about 15 BHN, but the same hardness can be got with 6 or 7% antimony and no tin. At that sort of hardness it will penetrate and expand a little without fragmenting. With gas checks it will not lead the barrel despite being quite soft at more than 2000FPS, but I can't tell you how much more than 2000FPS because I haven't tested it.

I am in the process of writing a book specifically about cast rifle bullets, so I am able to quote the results of my tests so far. None of this is new information, but it is worth knowing nonetheless. My tests are being fired in a Sako in 308 Win. I have fired plain base bullets up to 1800FPS to test the MV limit of a handgun powder similar to Unique. Chrono readings indicate that 1800 is pushing max. At 1400FPS leading was virtually zero, and 1600 it was minimal, but at 1800 it was too heavy to be acceptable. Antimony content was 12%, BHN similar to linotype.

I tested the same bullets fitted with gas checks with a rifle powder similar to 3031. The fastest I have pushed them is 2400FPS. The bullet weighs 169 grains with gas check. The primers indicate no excess pressure and the MV increase per grain has not started falling off, so I reckon I will easily get 2500FPS. Leading is zero.

But take note that my tests thus far have been to establish the limits of leading, and what max MVs can be expected with various powders. Until those tests are complete I shall not be looking for accuracy so I can't say whether velocities well over 2000FPS will be accurate. I can say with confidence that you will get 2400 without difficulty with all three calibres with gas checked bullets. Generally, weight for weight, cast bullets can be driven 5% faster than jacketed at the same pressure, or same velocity at 5% less pressure.

But if you want to push max I would advise not pressing your luck without a chronograph. Sometimes I feel the need to be cautious what I say to avoid teaching my grandmother to suck eggs, but for those who might not know, a chronograph tells us other things besides velocity. One of them is warning of approaching max. In my tests I am getting about 64FPS increase in MV for each grain increase in powder with powder similar to 3031. It is a linear increase, but I know that the first warning will be an increase of 50FPS and when I get 30 or 40 that's where I'll stop and back off. The importance is that when the MV increase slows, the pressure curve increases exponentially. That's the value of a chrono. I'm using a Chrony. Very accurate and reasonably priced.

If you want to reduce your alloy cost a little, you will find that 10% antimonial bullets will shoot quite well. To get that mix 66% of your alloy with 33% pure lead. Of course you are not likely to find pure lead at your local scrap yard but most scrap averages no more than 1% antimony so you can mix with scrap safely. Don't worry about watering down the tin. Tin is not needed for bullet alloy.

But for the long term why not buy scrap and blend your own alloy with antimony. You'll still have to buy the antimony from a foundry or specialist metals supplier but that's the most economical way to get alloy and you have complete control of the mix.

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CBA Member

Mike H posted this 13 October 2009

Hello James,

Thanks for the info re alloy supply. I still have a fair amount of wheel weights, but also a lot of sheet lead, that will need enriching one day.

Regards, Mike.

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Standard Member

biddulph posted this 11 October 2009

Hi Mike,

dont get too many from Wagga on this forum! Thanks for the info. I've been shooting wheel weights for some time, also chilled straight from mold to bucket of water at room temp (Darwin build up temp that is) also bucket full of ice water with resultant BHN's up to 14. Shoot really well too: .375 265 gr Lymans into 1,5” group at one hundred yards.

Just thought I'd go down the velocity path and see what happens.

I got the alloy from Consolidated Alloys in Melbourne. Its a 15 percent antimony, 5 percent tin mix. I've cut it down to linotype so as not to be too OTT already! Cost is about 5 dollars a KG, freight to darwin for 40 kg was 50 dollars, so if you cant find wheel weights or want to be sure about the percentages, I'd recomend them. Have to sort out some one to pick it up and get it on a bus for you though... I think they have a presence throught Australia, certainly in Sydney.

Cheers

James

Probably reinventing the wheel anyway, but there you go!

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CBA Member

Mike H posted this 11 October 2009

I would be inclined to cut that alloy with an equal amount of pure lead. Also throttle the loads back to 1800 to 2000 fps., then keep the ranges under 200 yards. If happy with the results, then try for more if you feel the need.

Mike.

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Standard Member

cityboy posted this 09 October 2009

I never thought of using a wood chisel to cut off the lumps. I am currently using a small V-block to file of base lumps.

I hold the bullet in the V with a finger to keep the base square. I tried doing it freehand, but my filing skills are not too good.

Jim

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Standard Member

biddulph posted this 09 October 2009

Casted some linotype bullets last night. City boy, you're right about the divits! Sprue bits on the end of 30% of bullets: cleaned up well using a sharp wood chisel: sliced them off very nicely and controlably.

Unsure how fast to push them, probably starting loads as per jacket in manual: 2400fps.

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Vassal posted this 02 October 2009

I just picked up about thirty pounds of Monotype. I was hoping to mix it with WW, or Soft,or soft and WW. I am not sure where to start. I havent done a great deal of checking, but Mono is a bit harder to find recipes for than Lino. I am looking for two alloys. 1=rifle@1700-1950(+/-)

2=rifle@2000-2500 (roughly)

Maybe even higher???? not often ,,,,,,, but maybe,,,,,,,I always push the limits at some point, though the thought of leading up my rifles makes me queesy.:puke:

EDIT:::___-------------------______----------------------

Since posting I found the “alloy calculator” excell spreadsheet!! That is great and takes care of many problems.

I “Always push the limits” to find what can be safely and sanely done, not anything more

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Standard Member

cityboy posted this 02 October 2009

Jeff Bowles wrote: I have some alloy, some call it monotype, but it came from a major Detroit newspaper when they converted to the new printing systems. We have shot this alloy at over 3000 fps with no leading.

However it tends to be brittle and some of the bullets fracture at the grease groove mid flight.

I have some mono and find it too hard for my needs. I tried casting with it; the fill was great, but when the sprue was cut it left a big divit. Mono is brittle and does not shear well.

Jim

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Standard Member

biddulph posted this 02 October 2009

Thanks a lot guys, this info is most useful.

I have loads of pressure info for .308 in both Lee and Lymans manuals but they don't include pressure info for .375 h h or .303 unfortunately.

I'll try starter loads and see how they go.

Hope your autumn is going well, we're into the sticky 'buld up' here, prelude to the wet season. Takes ages for barrels to cool down at the range. Will be comming ot US for Christmas vacation, into Seattle and up to Canada for a cool change.

cheers and thanks

James

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CB posted this 02 October 2009

I have some alloy, some call it monotype, but it came from a major Detroit newspaper when they converted to the new printing systems. I measured it and depending on which bucket of type I am using, measures 28 to 30 bhn avg from the Lee and LBT hardness testers.

We have shot this alloy at over 3000 fps with no leading.

However it tends to be brittle and some of the bullets fracture at the grease groove mid flight.

I shoot lead that tests out at 24bhn on a regular basis and I shoot it at 2200fps with no leading.

Hope this helps..

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CBA Member

tturner53 posted this 01 October 2009

I've been on a similar quest. Somewhere here there's a chart that relates bhn to how many psi a bullet can handle. I've heard of it but haven't seen it yet, but your alloy should handle some pretty high pressure. I'm working with a similar (more or less) alloy only based on ww so I can heat treat. I think it'll be more of a pressure limitation than velocity only. EDIT: Two formulas that may help; From Roto Metals website, BHN = 8.6 + ( % tin x .29) + ( % ant. x .92). Your alloy would be 23.85 bhn. From a reliable source to be used as a guide only (not chiseled in stone); ( BHN x 480 ) x 3= lower psi obturation begins. My figurin' says you can go up to about 34,344 psi with that alloy. For the record I'm only repeating information someone else figured out and can't say I know for a fact how accurate it is, but seems to make sense to me. hth tt

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high antimony alloy: how fast can I push it?

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