I was recently challenged by a more advanced caster here (45 2.1) to work to achieve near perfect consistency in my casting. I was told that if I do it right, I should be able to drop hundreds of boolits with less than .2 grains total deviation.
I realized that I have never really tested a casting session to see exactly what I do and how consistently I cast.
So I cast 100 boolits and proceeded to prove to myself that I am so far off the mark it aint even funny! Its true, I had many consistent boolit weights, but instead of just shrugging and throwing the culls back in the pot, I decided to record them. Not only that, but when I decided to only keep the boolits that landed in a .2 grain window, I basically ended up throwing more than half of them back in the pot. So I started lining them up on the bench according to weight in .1 grain increments. I have done this before, but I never tried to make sense of it, or put them in a row.
When I did, I saw that the boolits produced a bell curve of sorts. Literally a graph of my proficiency as a caster! The shorter and broader the curve, the worse I was casting. In contrast, the higher and narrower the curve, the better I was casting.
Let me walk you through what I did:
So this first graph was me casting at 700* with 50/50, in a Lee 20lb pot, with a brass MP four cavity mold, with a 10 second dwell after the drop.
Attachment 91247
I changed to a ladle and cast these
Attachment 91246
I then ran the mold hot and eliminated the dwell after the drop. Open and shut, peddle to the mettle.
Attachment 91248
Now, at this point, even though I was seeing improvement, another test I was doing was telling me that there was something going on with the mold. You see I had witnessed the cavities in the mold so that I could tell the boolits apart after they had dropped. Once the curve was established, I would take the best boolits out of the middle of the curve, and separate them into each of four cups based on which cavity they dropped from.......then I would weigh the cups of boolits to see if there was any correlation between a certain cavity and the boolits that landed in those two perfect strings in the middle of the curve. What I discovered surprised me.
Every time, with startling consistency, the last cavity filled was producing the most consistent boolits. In other words, the cup that weighed the most, was always directly related to the cavity that was last filled.
I tried and tried to think of why that might be. I called several people today and hashed the problem over. One of the people I called was Larry Gibson, and he speculated that the lead in the bottom of the pot, and especially around that spout, was cooler than the lead in the middle of the pot. This made perfect sense to me, because the spout has to be a source of heat loss since it's hanging out of the pot. He suggested that I might try putting an ingot mold under the spout and pouring some lead into it to "prime" the spout before filling the mold. He also suggested turning up the heat a little to 725*.
So I figured what the heck? I turned up the juice, and put my ingot ladle under the spout, preheated my mold, and began. I would pour into the ladle for two seconds and then sweep the mold under the spout and begin filling the mold in the same order that I did before. This had a dramatic effect on my boolit graph, as I ran the good boolits right off the paper in no time and the discrepancies were reduced significantly.
Attachment 91252
Im still not there, but I realized that this trick can be used to find out all kinds of useful information about your casting technique, and where the weaknesses are in your method, as well as showing you in real time how effective a theory is.
I want to extend a big thank you to Sergeant Mike as he was here with me for 6 hours today and helped me run these tests. He had a theory that if we used his Seaco lead pot, ran the melt at 875*, and pressure cast the boolits, then we would get better consistency. We tried it, and this is what the graph looked like:
Attachment 91253
It was easy to see that method was not going to work. The numbers just don't lie.
Ideally, what I will strive for is to be able to cast 400 boolits and have only two rows of boolits as long as my bench, and two rows of boolits about 5 deep. That would be near perfect casting for all intents and purposes.
I hope this trick will help you to see your consistency and help you diagnose problems in your methods.
It sure was an eye opener for me!
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Originally Posted by goodsteel
