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Lead Pot temp

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OK, I have a new Lyman Lead thermometer. Up until now, I have been flying blind.
So far, I have found that 750-800 and a warmed up mold seems to be a good temp range to heat up the lead to mold. I was surprised that the setting I had it on heated it up to almost 900F. I got the thermometer so I can try to keep the temp consistent from both within the batch and from batch to batch.
Right now, I have been working on some .578" minie balls using a Lyman Mold which is aluminum.
I'm concerned about both fill and shrinkage, but I have some sizing dies on the way so I can size the bullets to my guns (.580", .578" and .576" dies on the way)

How does mold as well as lead temp affect shrinkage and fill?

I'm using pure lead with Brinell harness of approx 5.0 (using Lee hardness tester)
Hmm, you look like someone I know. :D
 
I have been casting Minnies since about 1972, and had got quite good at it. After eyeballing for visual faults, find only a 3 to 4 grain variation.
I moved my lead casting set. up into my smithy a couple of years ago, then all of a sudden found was getting a shrinkage runnel coming up from the base plug as against a shrinkage runnel from the nose down if I did not leave enough of a puddle on the sprue. I was using mostly 99.97 pure BHP ingot lead, still the same problem. I have cleaned out the pot and ladle, still seems temp related. The only thing might be that my new set up which is a house brick surround 3 sides of the pot and an cement top with a large hole in it. This latest version might be more heat efficient, not sue. Have just purchased an infrared heat gun -50 to 1200 'C that might tell me just how hot it is getting (cast iron gas ring). When I let the mould cool (brass blocks and steel base plug) I seem to get a better result, but now have a much greater variation in weight, 5 to 9 grains after eyeballing. Have not changed my pouring tecknique ., Same issues with my cast iron Minnie mould and my brass Pritchett bullet mould.
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I use the Lyman 10# pot with the dipper and thermometer. 750-800° works the best for me, too. The BPCR crowd especially seems to have this process down to a fine art, given their shooting tends to be out to 1000 yards at times. I read an a thread written by one of the top BPCR guys, who uses a PID controller to keep his lead temps pretty precise. He found that a raising or lowering the temperature by 5 degrees produced a repeatable 1-grain change in average weight in a 400g mold.

http://www.bpcr.net/forum/viewtopic.php?f=6&t=7996
Of course, that's a minor percentage of total weight. But if your temp drifts 75 degrees without you knowing it, you can certainly get some large-enough variations to affect accuracy. I would imagine the results of such variation are more impactful on Minies or other conical than on roundballs, but I don't really have a firm basis for that assumption.
 
Been casting since 1972. Started with a Lyman cast iron 10lb. pot, a propane torch and a Lyman dipper. Today I use a LEE 20lb. bottom pour pot and a PID controller. The PID controller is one that I made. I keep the set temperature at 630 degrees for pure lead, 1% tin/lead alloy and Lyman number 2 alloy. Always have excellent fill out. The PID keeps the temp to within 2 degrees of the set temperature. The attached picture is a PID that I made for a friend and I'm testing it with my other LEE 10lb. pot.
 

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I've been casting round balls, centerfire pistol bullets by the 1000s, and minie balls for over 40 years. I save my thermometers for cooking ham and such.

Always go by if it pours and fills out well it's hot enough. Frosty bullets is too hot, wrinkled or not filled out too cold. I cast from multiple molds at one time so the sprue gets hard and doesn't make a mess. Never needed a hot plate.

That's all Folks.
 
I have cast minies and round balls for forty years with a Lee bottom pour and various molds. Run the gauge between 7 and 8, pure lead, and a good cadence. After five to ten warm up casts, I am ready to run ball or bullets for production. I inspect and weigh all; if I am in the groove, I have very few rejects after the first ten; when I add lead to the pot, I always give it time to come up to full temperature, flux and skim to remove junk from the top, and go back to work.

I have found that if the Lee Pot is left too full when I am done casting, when I re-heat to start again I can get a runaway spout. The rod that blocks the bottom pour spout seems to get hung up and not drop into place. That is why I always have an ingot mold under the spout, and never let it heat up unattended. I can usually stop the runaway by tapping on the top of the rod with my leather casting mallet.

I have two of the Lee pots, one for alloy and one for pure lead only.

ADK Bigfoot
 

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