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oughtsix
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casting temp vs bullet size
Apr 6th, 2019 at 8:55pm
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What is the rule of thumb for casting bullets at different temps?  the inter webs  seem to be ambiguous.  The late Frank Zika said high pot temps make small bullets.  Texasmac's recent casting experiment  seems to look like higher temps make higher weights, at least using his alloy (15.7:1).

Is there a chart of alloy temperatures vs bullet sizes?


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Re: casting temp vs bullet size
Reply #1 - Apr 7th, 2019 at 2:52am
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I believe the best conclusion is that the difference is so small it is negligible...  And I would personally look a mould temp as being the main factor for that (negligible) difference.  But then, we don't monitor/control mould temps accurately.
  
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Re: casting temp vs bullet size
Reply #2 - Apr 7th, 2019 at 9:42am
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I've played with it a number of times.  When I cast, lower temperatures make lighter bullets every time.

The difference in diameter is very small.  On the order of a couple of ten thousandths.  This is what would be expected.  To give you an idea of the diameter change expected, just calculate the mass of a lead cylinder that is the same length and diameter as your bullet, then compare that to one that is a half thousandths larger.

Chris.
  
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Re: casting temp vs bullet size
Reply #3 - Apr 7th, 2019 at 3:33pm
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gunlaker wrote on Apr 7th, 2019 at 9:42am:
I've played with it a number of times.  When I cast, lower temperatures make lighter bullets every time.

The difference in diameter is very small.  On the order of a couple of ten thousandths.  This is what would be expected.  To give you an idea of the diameter change expected, just calculate the mass of a lead cylinder that is the same length and diameter as your bullet, then compare that to one that is a half thousandths larger.

Chris.

Chris, At what temps are you using to get the variations?
  

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Re: casting temp vs bullet size
Reply #4 - Apr 7th, 2019 at 4:09pm
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I've done a few experiments all on the same day and same batch of lead.  I started with a batch at 775, another at 800, and the last at 825.  This is with 16:1 and cast in a Buffalo Arms mold ( with the big Saeco blocks ). 

The bullets were all good and filled out, but the lower the temperature of the batch the lighter the bullets.  I don't remember the numbers, but not a lot, maybe a grain or so difference between the batches if I recall.

I didn't test the mold temp, but the alloy temp though. 

Chris.
  
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Re: casting temp vs bullet size
Reply #5 - Apr 7th, 2019 at 4:25pm
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I cast at 800 to 820 anything lower than does not completely fill out the mould cavity based on my own personal experience. Often times they will also not come out nice and round and the blame will be put on the maker of the mould instead of the end user.
  
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Re: casting temp vs bullet size
Reply #6 - Apr 7th, 2019 at 10:12pm
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I cast with a mold temp of 410 to 415, if it drops to 399 or lower, there will be a lower weight.  I used to cast at 800 to 825, but I dropped to 775 to speed things up.  Too much time spent waiting for the mold to cool. I didn't weigh any bullets when i changed.  Now y'all got me curious  Undecided
  

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Re: casting temp vs bullet size
Reply #7 - Apr 7th, 2019 at 10:38pm
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Bob I imagine my mold temperatures probably changed a bit at each lead temperature setting, although I did cast with a faster pace at the lowest temperature.

John one of the differences may be that most of my molds are made with the big Saeco blocks which hold a lot of heat.  They definitely fill out very nicely at 775.  I don't know if I could ever use a Hoch mold at such a low temperature though, or even my Steve Brooks molds.

With the smaller blocks I run hotter and cast as fast as possible.   

Chris.
  
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Re: casting temp vs bullet size
Reply #8 - Apr 8th, 2019 at 12:11am
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Chris, That is a Hoch mold I was speaking of in the previous post. The vast majority of the bullets I have cast in the last 10 years have been with it.
  

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Re: casting temp vs bullet size
Reply #9 - Apr 8th, 2019 at 9:21am
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Bob now I am going to have to play with the temperature when using my Hoch molds.  With those I've been using a little over 800 and even then I'd say I cast twice as fast as with the big molds from Buffalo Arms.

I have a lot less experience casting with the Hoch molds than I do with the Buffalo Arms ones.  I will say that once the Hoch ones come up to temperature they are pretty amazing.

Chris.
  
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Re: casting temp vs bullet size
Reply #10 - Apr 8th, 2019 at 10:20am
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Quote:
Texasmac's recent casting experiment  seems to look like higher temps make higher weights, at least using his alloy (15.7:1).

Temperature of the melt primarily determines whether the bullet is frosted or not.  High melt & mold temperatures drop frosted bullets

Within the proper casting temperature, the alloy being used determines lighter or heavier bullets.  Good source of information is LASC Cast Bullet Notes ... (You need to Login or Register to view media files and links)

Good example in my case: Paul Jones 45-70, 535gr nominal mold:
* 539gr average weight - Pb & WW's with antimony mixed to a 1:20 alloy
* 542gr average weight - Pure Pb & Sn mixed to a 1:20 alloy
  

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John
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Re: casting temp vs bullet size
Reply #11 - Apr 9th, 2019 at 9:27am
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Casting tempreture is not a one size fits all thing. It depends on many factors the size of the bullet, the size of the blocks, the material of the blocks, and the speed of your casting. Generaly I run my molds as hot as possible without sticking when they stick I have to turn down the pot a little. Generally the smaller the bullet the hotter I run the pot.

40 Rod
  
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