Why there a different weight of bullet from top of pot to bottom pour?

[Fletch6]

I am new to trying my hand at casting some bullets for black powder.  I got an old melting pot with a bottom pour lever and have noticed something that is strange to me.  I had some old lead diving weights that I have not used in years and that I think are almost pure lead that came from elect. cable connectors.  I got a REAL 250 grain mold and started pouring from the bottom.  I was getting about 4 grain vairation of weight between 248 and 252.  some one said that he only dips and pours and when I tried this got a 255 or 256 grain bullet.  The bullets made from the top of the 10 lb. pot give me a heaver bullet.  I am putting a dip of flux in to remove slag.  Could this be changing the lead at the top of the pot?   

[Lloyd Smale]

What can happen is as your pot gets down the lead has less surface area to heat and loose heat from and can get hotter. this intern can actually give you better bullet fillout and slightly heavier bullets. Bottom line though is you will never seen a differnce in point of aim or accuracy with a 5 grain variation in a 250 grain pistol bullet anyway.

[Fletch6]

Actually the bullet is for a 50 cal. Muzzle loader, but what you have said does make sence.
What I was trying to explain is the pot is about 10 lbs of lead and when I dip from the top
the lead pot I get the heaver bullet and the weight is more consistant. the bottom pour
is the lighter bullet and given that heat rises and it would be cooler at the bottom seems
to not pour as good. I.E. more vairation of weight and lighter.

[stimpylu32]

Fletch6

Also your pot full may be seperating as you use it , even with so-called pure lead it will have some other metals in it , like Tin that will float on top of the lead , you may want to mix it as you work every so often just to keep it consistent .

stimpy

[Graybeard]

Technique is the answer. Ya do it two ways and ya fill it out a bit different using the different techniques. As Lloyd said you'll never see the difference on target.

[Larry Gibson]

Lloyd and Graybeard are correct.  However the difference in weight is caused by the alloy not getting into the mould as fast as with a dipper.  The alloy, even close to pure lead, starts to cool and harden as soon as it touches the mould. Thus the faster it gets into the mould the better the fill out is and the more consistant and heavier the bullet.

Solutions are;

Continue to use ladle if you want.
Open adjustment on bottom pour to allow alloy to come out faster.
Increase casting temperature of alloy.
Cast faster keeping the mould hotter.

I will use my bottom pour (Lyman Mag20) for bullets up to 300 gr.  Over that and I use a ladle. 

Larry Gibson

[Lloyd Smale]

larry makes a good point. Another thing if you insist on ladle casting get a good ladle from rotwell they hold enough lead that it isnt cooling before you get it to the mold. The MOST important thing in bulllet casting is your rythmm. If you want good bullets you have to go consistantly and smoothly.

[Fletch6]

OK and thanks for the feedback.  I might give the larger ladle a try. It does seem that the lead is cooling in the small ladle to quick to pour twico in the mold.  I was surprised everyone feels that a 5 grain difference is not enought to change POI and accuracy.  I was trying to keep within 2 grains thinking it would make a difference.

[pourboy]

I ladle cast. I tried using the bottom pour, but wasn't satisfied with the process. First of all, I had large weight differences with bottom pour, much like you are describing. I also has much poorer "fillout" with bottom pour, my bullets didn't seem to always fill out completely, there always seemed to be something not quite right, often an incompletely filled out band at a lube groove. So I tried the ladle. I had nothing to lose, I had already made up my mind to quit casting if I couldn't produce uniform, quality bullets.

So I bought a ladle, and converted it to left-hand use, and went to it. The first thing I noticed was my bullets were slightly heavier. They were uniform & well filled out (this is the short version, it required some experimentation to get to this point). With the bottom pour I had little black specs in some of my bullets, and these bullets were always lighter than the miserable few "good" bullets I produced. I would melt these bullets down to find out what the contaminant was, but there was never anything there but lead.

I finally came to the conclusion that I was aerating the alloy when I used the bottom pour. The specs I saw were tiny air bubbles. I had tried both a LEE bottom pour, and a Lyman, with the same results. When I ladle cast, I only fill one cavity at a time, and pour the excess lead from the ladle over the hole in the sprue plate, like I was still trying to fill the cavity. I think this keeps the bullet somewhat molten, and allow air to escape over a longer period of time. I feel this is what gives me heavier bullets, with much greater weight consistency, and such greater quality.