A funny thing happened at the bottom of the pot

[piwo]

Well, not laugh out loud funny but perplexing. On Saturday I cast .530 roundball for a couple hours and was actually marveling at the consistency I had been achieving. While the stated .530 roundball weight for pure lead is listed at 224gr, my mold was throwing out a very consistent 225.5 gr roundball. Cast well over a hundred and finally allowed the pot to run down to the bottom. It's an electric bottom pour rig. Well, the last "batch" as I let the pot empty out surprised me. I monitor temperature and cast my pure lead @ 950 degrees and I kept vigilant that the temp didn't skyrocket as the pot emptied. After the balls had cooled, I weighed them (as is my methodology to discard light balls) and I found that after casting near 200 at 225.5 gr, I was now gettting 226.5 - 227 gr. Not a single ball weighed that much in the first 2 hours and then the last batch was full of them. I first thought "crud" in the pot, but crud would weigh less I would think.

Anyone experience that??

[stubshaft]

I have never had that happen to me. How about turning your theory around and suppose that the initial balls had impurities in them and as the lead cooked the impurities were minimized by the time you reached the bottom? OR Have you measured the diameter of the heavier balls? Could have gotten some gunk on the mold face making the ball slightly larger.

[451 Pete]

A lot of possibilities here. One grain of lead is not very much material.
A sprue plate coming a little loose, a small particle of lead on the face of the mold, the thermometer not catching small temp. increase's as the lead amount decreases. Were you returning the sprues back into the pot? Did you break the rythum in your casting as you became tired? It does not take a lot to vary weight by one grain. This is the reason I only cast down to the pot being half full.

Just my thoughts .... Pete

[piwo]

Thanks for your input guys. The thought that the initial balls were "light" crossed my mind, but sooooo many and they actually weigh over the "stated" weight for .530 RB's led me to believe I was good there. I did measure the balls and inspected the mould and all seemed in order. It's possible my temp increased at the very end, but not for too many RB's, but a few. And I did get one or two light ones that were discarded and let me know that I got air bubble or crud. Other than that they were all shiny, smooth and beautimous! I'm thinking the sprue plate as I did tighten it down once or twice as it seemed to loosen up during the process but that didn't occur to me as a cause for heavy / light result.

So with these and the .680's for my shotgun I ususally pour a generous amount of overflow on top of the sprue hole as I read from someone here that it helped keep the top from setting up as the larger ball did so. Good practice?

[telebasher]

Interesting thread to us that use the Holy Black to be sure. My question is how much difference in POI does one to one and a half grains bullet weight make at 50 or a 100 yds and can you "hold" less than that difference offhand ? One to one and a half grains to a 54 cal roundball is less than 1%. My 54s would shoot into an inch and a half benched with younger eyes @ 100 yds and on a good day 3 inches offhand. Alas those days are long gone. How much accuracy are you capable of?

[piwo]

I can't imagine it would make any tangible difference, provided one of the two wasn't light because of an off center "air void" or bubble. Anything that would send a ball spinning untrue would certainly be potentially altering, but two perfectly balanced balls with less than a one half of one percent difference in weight wouldn't amount to a hill of beans.

I guess I'm scratching my head more as to the "why", and for snickers and grins I've kept them all: in two groups. Thems that weigh in .225.4 - 226.0 range and thems that weigh in the 226.4 - 227.0 range. I'll shootem in groups of 5 and see if there's anything at all perceptively different. If it's just a difference in sprue, I'm betting there won't be any. If the lighter ones don't group as well, then I'll lean towards the "i must have some void" theory.....

Going out on Saturday or Sunday, time will be the constraint if I get to do the complete test. I'll be hunting on Monday evening if things work out and so I need to make sure I've got a "cold proof" lube working well with patch and ball. I fear my wax based lube on patch might not be the best for freezing temps. If you have any thoughts to share on that I'd be happy to receive them!

[fishhawk]

well the .562 RB for my .58 according to things should weigh in at 267.5 gr if i get them 265 or better i keep them. that couple gr. in a round ball with volume measure for powder isn't going to amount to a hill of beans.