Mold Temperature

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  • Last Post 04 July 2022
Wm Cook posted this 01 July 2022

Is it common knowledge that what a mold temperature is effects the weight of the bullet that it drops?

That if you cast with an external mold temperature running 370, that it will cast bullets lighter than if the mold was running say at about 405. Example 214.5 @ 370 vs 215.2 @ 405.

Zip, zero, none, nada insinuation that light vs heavy or mixing and sorting would have any effect on accuracy. Or if it even makes a difference for any practical reason what’s so ever.

Just a question about what the general consensus is about mold temperatures and it’s effect on cast weight.
Thanks as always, Bill Cook

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RicinYakima posted this 01 July 2022

Well, .00325% of weight change is not going to make must difference under 14,000 yards. 

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RicinYakima posted this 01 July 2022

How many angels can dance on the head of a pin?

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Wm Cook posted this 01 July 2022

Agreed 100%. It will make no difference.

Just a question about what the general consensus is about mold temperatures and it’s effect on cast weight.

If there’s no opinion because no one has looked at or no one is interested in the effect of mold temp and weight, that would be a valid answer. Thanks, Bill C.

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Bud Hyett posted this 01 July 2022

My latest experience is the mold temperature and alloy temperature are a factor in casting consistent bullets. The mold temperature is dependent on alloy temperature and speed of molding. I've used an infrared digital thermometer in the past to check mold surface, but the readings were never consistent enough to set a standard in my opinion. The surface temperatures were in the high 300 degree range slowing going to the low 400 degree range, but without affecting the weight or diameter of the bullet. .

I've gone to the newer RCBS ladle pot with digital readout to stabilize this. The results are far better weighing and looking bullets resulting in better scores. The range of weight now is +/- .2 grains on a 208.5 grain nominal bullet.  

The old approach was my old RCBS Pro-Melt, run it wide open with two molds. Variation was +/- .1.5 grains with a large portion with +/- .003. I'd run a pile of bullets for four or five hours and then weigh to sort them. The lighter bullets were set aside for sighting in. This is too labor intensive.  

 

Farm boy from Illinois, living in the magical Pacific Northwest

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TRKakaCatWhisperer posted this 01 July 2022

excellent question.  I have several molds drilled for a thermocouple; someday I'll stick one in and monitor mold temp.

 

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gunarea posted this 01 July 2022

Hello Wm Cook

    Your question is valid, however, the answers are relative only relatively. I'm a good ole, redneck, country boy. Also an accomplished road and bridge engineer. Competitive shooting is my lifelong hobby and obsession. In my sixty years of chasing gold, close enough, never delivered first place. 

    You have part of the equation correct. Now expand the logic. Same mould, same sizer, same case, same charge, same same all. Different weight will not have same point of impact with identical point of aim. Simple physics. Small weight variation gives small impact variation. My studies have been exhaustive, extensive, aggravating, interesting, productive, and 47 other technical words and assorted terminology.

    External mould temp, internal mould temp, ambient temp, average molten alloy temp, discharge spout temp, heat sink temp, metronome, single cavity mould, 4 assistants tending to various aspects and two just for recording. The rabbit hole is just so deep as the victim allows it to become. 

    When close enough will suffice, the difference is negligible. When precision is sought, much more diligence is required. Simple!

                   Roy  

Shoot often, Shoot well

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Wm Cook posted this 01 July 2022

Getting anal about something that everyone believes is unnecessary should fall under the protective umbrella of:

“Do the same thing the exact same way every time”.

From prepping brass to taking the recoil at the bench successful reloaders/shooters try to do the same thing the same way every time.

Not many will dump on that philosophy because it’s a motherhood statement. And Motherhood, God and country are usually protected from rocks and stones.

That said I think I’m close to having hard data that will show the relationship between mold temperature, alloy temperature, weight of bullet and the range of bullet weights being dropped. I need a couple more casting sessions to see if I can duplicate my methods.

But getting back to the ordinal question. I was hoping that there was some history that had left a trail of information about mold temperature management.

Note: I’m not looking to getting into a shooting war over the relationship between bullet weight consistency and accuracy. I just want to know more about mold, alloy temperature and their impact on the bullet coming out of the mold.

Thanks for listening, Bill C.

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TRKakaCatWhisperer posted this 01 July 2022

Coool!  It is likely that there isn't much history of mold temp vs [insert variable] because of the instrumentation.   NOW we have commonly available digital temperature measurement and temperature control.  Previously, it was a matter of controlling/stabilizing mold temp by regulating the times of pouring and cooling.

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MP1886 posted this 01 July 2022

I'll agree with what Bud said, he was dead on the money.  I'll add bullets that  aren't all the same weight are DIFFERENT from one another and that's not a good thing.  I feel the weight difference becomes a problem in grouping when it's to the left of the decimal point or damn close to it. 

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Wm Cook posted this 01 July 2022

I was hoping to avoid this going into the "Must Weight" versus "Weighting Not Needed" camps but I guess it was inevitable.  That said:

  • I have seen data that showed that weighting to the tenth of a grain had no impact on accuracy.
  • I have not seen data that showed by weighing to the tenth of a grain has an impact on accuracy, but I always have an open mind and willing to learn.

My focus has been on whether mold/alloy temperature has an impact on bullet drop weight.  After the last 6 or so casting sessions I'm close to saying that there is data that supports that a mold at x temperature will yield a bullet heavier or lighter than a mold at y temperature.

Once I understand the effect of mold/alloy temperature there will be 10 shot groups shot with like "light" bullets, 10 shot groups shot with "heavy" bullets and 10 shot groups shot with a mix match of heavy/light bullets.  My expectations for finding anything different than what others have found is not that high.  In other words, that a few tenths of a thousands ("few" defined by the user) has no effect on accuracy.

What I am interested in seeing is 10 shot groups shot with bullets coming from the same mold temperature.  Which if found to be a positive effect on accuracy will create an aura of magic/mystery around the metallurgical fusion of of the cast alloy at x temperature.  Understanding that is way above my pay scale. 

Thanks, Bill Cook (obviously retired, A+ personality and it appears that I have too much time on my hands)

PS: To keep this into perspective: "Accuracy requires the user to be using match grade casting, reloading and bench equipment and match grade casting, reloading and bench practices".

 

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Aaron posted this 01 July 2022

What follows is PURE SPECULATION.

I don't think a 50 degree mold temperature variation will affect bullet weight, all other things being equal, unless that 50 degree variation is near the liquidus temperature of the alloy which generally is a lot lower than the casting temperature. Temperature variation may contribute to wrinkles, voids, and such, which will affect bullet weight of course.

I think you are inferring that casting temperature variation of the mold will affect bullet size and therefore bullet weight. The minuscule size variation of a mold cavity from a 50 degree variance is all but immeasurable and that variance has an insignificant affect on bullet size and therefore weight. Of much more significance to where that bullet may strike with a .0003gr difference in weight is your optical acuity. cool

 

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delmarskid posted this 01 July 2022

and then I wonder about grip strength on mold handles

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John Alexander posted this 01 July 2022

Bill sez: "Once I understand the effect of mold/alloy temperature there will be 10 shot groups shot with like "light" bullets, 10 shot groups shot with "heavy" bullets and 10 shot groups shot with a mix match of heavy/light bullets."

Excellent idea. I will be very interested in your results.  Great idea for another thread. It would be nice if all the posters above who believe minimum bullet weight variation is important for good accuracy would all shoot a similar test. It would be interesting to see the results. Sort of a cooperative joint experiment. I would be happy to participate if there is any interest.  Pretty easy to do even if two ten shot groups of each condition. I won't hold my breath. It is easier to just "know" something, and it may be threatening to put what one knows to a test.

John

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Hornet posted this 01 July 2022

   I've done a LOT of weight sorting, not so much trying for absolute uniformity but trying to eliminate the outliers at the high and low ends of the weight distribution bell curve (which has some skew in it with castings). I've found that if I interrupt a casting run for a few minutes and the mold cools a bit, I will get slightly lighter bullets for the next few pourings until things come back up to a more stable temperature. The lighter ones don't need to have any visual defects or porosity explain the weight difference. The ones that I've checked are frequently just a touch ( on the order 0.0005" or so) smaller in diameter and probably length. This COULD be from the material in the sprue solidifying slightly sooner and not feeding metal into the cavity as the bullets shrink while solidifying. I have seen that happen in injection molding plastic when the fill & pack-out times are cut back too far. I usually toss the first 5-6 pours back into the pot and that seems to get rid of most of them.

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MP1886 posted this 02 July 2022

Bill sez: "Once I understand the effect of mold/alloy temperature there will be 10 shot groups shot with like "light" bullets, 10 shot groups shot with "heavy" bullets and 10 shot groups shot with a mix match of heavy/light bullets."

Excellent idea. I will be very interested in your results.  Great idea for another thread. It would be nice if all the posters above who believe minimum bullet weight variation is important for good accuracy would all shoot a similar test. It would be interesting to see the results. Sort of a cooperative joint experiment. I would be happy to participate if there is any interest.  Pretty easy to do even if two ten shot groups of each condition. I won't hold my breath. It is easier to just "know" something, and it may be threatening to put what one knows to a test.

John

 

It's not a logical test at all.  He'd be shooting bullets that all weigh about the same. A better test would be to shoot  a group with some that weigh the same and then shoot a group with a mixture of different weights.  An analog would be, for an example, you have a  223 and you have jacketed MATCH bullets of various weighs, preferrabley from the same manufacture.  Let's say 53 gr, 55 gr, 62 gr, and 70 gr.  Now if you were to shoot a group using all one weight, but what would happen if you shot  3 of each into one group.  Do you think the group would be the same as the groups shot with only one weight?  Bill's wasting his componants.  

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John Alexander posted this 02 July 2022

 

It's not a logical test at all.  He'd be shooting bullets that all weigh about the same. A better test would be to shoot  a group with some that weigh the same and then shoot a group with a mixture of different weights.  An analog would be, for an example, you have a  223 and you have jacketed MATCH bullets of various weighs, preferrabley from the same manufacture.  Let's say 53 gr, 55 gr, 62 gr, and 70 gr.  Now if you were to shoot a group using all one weight, but what would happen if you shot  3 of each into one group.  Do you think the group would be the same as the groups shot with only one weight?  Bill's wasting his componants.

=========

You and I must have a different definition of logical. It is common for CB shooters to weight sort their bullets to less than one  tenth of one percent variation ( 0.2 grain in 200 grain bullets) to shoot groups of unsorted bullets that might vary 0.3 to 0.5 percent vs. sorted bullets to see if sorting is improving groups or whether it is a waste of time is a great example of acting logically.

On the other hand, shooting groups with a mixture of 53 and 70 grain bullets as you suggest (a variation of 30 percent  -- 300 time more than sorting 200 grain to 0.1%) seems frivolous because that isn't answering the question (is sorting  to 0.1 percent worthwhile). Additionally, most shooters find out early on that if they change from 150 to 180 grain bullets in their 06 they had better find a new zero. So any knowledge shooter already knows the answer to your proposed test.

John 

 

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MP1886 posted this 02 July 2022

 

It's not a logical test at all.  He'd be shooting bullets that all weigh about the same. A better test would be to shoot  a group with some that weigh the same and then shoot a group with a mixture of different weights.  An analog would be, for an example, you have a  223 and you have jacketed MATCH bullets of various weighs, preferrabley from the same manufacture.  Let's say 53 gr, 55 gr, 62 gr, and 70 gr.  Now if you were to shoot a group using all one weight, but what would happen if you shot  3 of each into one group.  Do you think the group would be the same as the groups shot with only one weight?  Bill's wasting his componants.

=========

You and I must have a different definition of logical. It is common for CB shooters to weight sort their bullets to less than one  tenth of one percent variation ( 0.2 grain in 200 grain bullets) to shoot groups of unsorted bullets that might vary 0.3 to 0.5 percent vs. sorted bullets to see if sorting is improving groups or whether it is a waste of time is a great example of acting logically.

On the other hand, shooting groups with a mixture of 53 and 70 grain bullets as you suggest (a variation of 30 percent  -- 300 time more than sorting 200 grain to 0.1%) seems frivolous because that isn't answering the question (is sorting  to 0.1 percent worthwhile). Additionally, most shooters find out early on that if they change from 150 to 180 grain bullets in their 06 they had better find a new zero. So any knowledge shooter already knows the answer to your proposed test.

John 

 John, for God's sake, that  was an exagerated analogy.  I've weight sorted bullets and doing so DOES MAKE A DIFFERENCE.  But I'm not going to do a big test and waste my time and componants to prove it to  you gentleman. I still stand behind my statement Bill's wasting his time and componants.  Any knowledgeable reloader would know if you shoot bullets that wieigh very close to one another are going to shoot better then shooting various weights. It doesn't matter what the bullet material is made of. 

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John Alexander posted this 02 July 2022

MP 1886,

Everybody knew the earth is flat, the sun revolves around earth, a lead ball will fall faster than a wooden ball, it is simple logic or observation. People using experiments showed all these known facts were wrong.  

Believing that sorting bullets to 0.1% makes them shoot better groups than unsorted bullets that may vary two or three times as much is apparently just as obvious to you, and a lot of other shooters as well -- and just as wrong. This isn't just my opinion it is the result of wasting components to find out.  I have done dozens of cast bullet tests similar to the one Bill proposed and haven't been able to find what you think you know.  Berger Benchrest bullets varying 1.4% in weight (28 times larger than the 0.1% CB shooters sort to) averaged 8-five shot groups into about 0.3" at 100 yards.

Even Aristotle, a guy far smarter than you and me, "knew" that women had fewer teeth than men. Since he knew THERE WAS A DIFFERENCE he didn't need to waste time counting his wife's teeth to find out the truth.

The world isn't as simple and transparent as we would like it to be and we don't know everything we think we know. 

John

 

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MP1886 posted this 02 July 2022

MP 1886,

Everybody knew the earth is flat, the sun revolves around earth, a lead ball will fall faster than a wooden ball, it is simple logic or observation. People using experiments showed all these known facts were wrong.  

Believing that sorting bullets to 0.1% makes them shoot better groups than unsorted bullets that may vary two or three times as much is apparently just as obvious to you, and a lot of other shooters as well -- and just as wrong. This isn't just my opinion it is the result of wasting components to find out.  I have done dozens of cast bullet tests similar to the one Bill proposed and haven't been able to find what you think you know.  Berger Benchrest bullets varying 1.4% in weight (28 times larger than the 0.1% CB shooters sort to) averaged 8-five shot groups into about 0.3" at 100 yards.

Even Aristotle, a guy far smarter than you and me, "knew" that women had fewer teeth than men. Since he knew THERE WAS A DIFFERENCE he didn't need to waste time counting his wife's teeth to find out the truth.

The world isn't as simple and transparent as we would like it to be and we don't know everything we think we know. 

John

 

John old chap, you make it so easy to insult you, BUT I WON/\'T. 

 

How do you know Aristoltle was far smarter than you or I.  That's just your assumption.  If we could bring him back and put the three of us through a rigid IQ test in areas of study he may not have been.  

What does it prove with you shoot those weight sorted bullets, sorted to say .10 or less when you don't have anything to compare too unless you shoot the group with mulitple weight bullets!!!!!

I've done tests and I found out what works and doesn't work.  John cast bullets that don't weigh the same can often have a flaw you can't see.  Such as a small void. I agree that many benchresters don't weight their bullets.  I''ve seen data on that that makes some of them seem worse the bad cast cast bullet, but I doubt they will have a flaw. 

John I don' t shoot the velocities that most of you all here shoot. My development has been high velocity cast shooting.  With that everything has to be "right". 

 

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John Alexander posted this 03 July 2022

Without evidence or facts a discussion turns into hot air.  Let's agree to stop further hijacking Bill's thread.

John

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