Dip-Casting Bullet Weight Experiments

[TexasMac]

I just posted an article titled, Dip-Casting Bullet Weight Experiments. For some time I’ve been unsatisfied with the variations in bullets weights when dip-casting bullets for my Browning .40-65 BPCR. So I ran some experiments to identify the root cause, which turned out to be a success. For the details click on the following link: http://www.texas-mac.com/Dip-Casting_Bul...ments.html

Wayne

[desert deuce]

I just posted an article titled, Dip-Casting Bullet Weight Experiments. For some time I’ve been unsatisfied with the variations in bullets weights when dip-casting bullets for my Browning .40-65 BPCR. So I ran some experiments to identify the root cause, which turned out to be a success. For the details click on the following link: http://www.texas-mac.com/Dip-Casting_Bul...ments.html

Wayne

[desert deuce]

clicked on the link, got this message

The webpage cannot be found

[Gunlaker]

Wayne, I have never seen this effect personally. When casting for the recent match in Phoenix I cast 400 bullets in batches of 100. I generally don't use the first few bullets from each batch as they are light, but appear perfect.

All batches had the same average weight. Three were within +/- 0.3gr and the other was +/- 0.4gr.

I'm using a Lee 20 lb furnace and dipping. I make no effort at stirring, and keep the ladle submerged, except the spout itself which I keep protruding from the melt to prevent a buildup of "dross". This generally makes better bullets for me.

I'm no metallurgist, but I was under the impression that our alloys of lead and tin should exhibit no stratification. Is this incorrect? I can't find any references anywhere.

thanks,

Chris.

[Lumpy Grits]

I ladle cast, and make a point to stir the bottom pot with it before pouring the bullet.
I also put the ladle back in the pot, as the bullet sets up. Have no problem hold'n +/- 1gn weight with my 2, PJ .45 cal. moulds.
I do not use a PID. Just keep'n a close eye on the temp.
I return the sprues, when adding more alloy.
Gary

[TexasMac]

I posted the comments and the link to my article on several other BPCR forums & received a couple of responses that has me 2nd guessing my conclusion from the experiments. Both responders indicated that when tin is alloyed with lead, the result is a homogeneous mixture or solution, meaning the tin cannot separate, stratify & form a higher concentration in the upper portion of the pot as I suggested. Since additional research on the subject indicates that to be the case, I’m scratching my head and may have to run some more experiments to figure out what’s happening. There is a possibility that some of the weight changes could be related to a temperature stratification issue, but there’s no question that the percentage of tin in the alloy dropped throughout the casting sessions when the pot was not stirred. Regardless, stirring the alloy still applies.

Wayne

[Gunlaker]

Wayne I understood that the mixture should be homogeneous, but I don't have any references to say whether in practice that is really the case or not. I sent some time "googling" but came up empty.

I do like the idea of measuring the SG. I remember the article you wrote in the BPCN a couple of years ago and thought it was quite interesting.

Chris.

[Lumpy Grits]

I cast at 760*-770*. At least that's what the thermometer says. It could be higher or lower temp.
Have seen Tin start to discolor the top of the melt when I have let the melt temp get away from me and get up to the 800* mark.
I did find my bullet weight consistency to really improve, when I started 'deep-stirring' the melt before I pour.
G.

[TexasMac]

Due to the previous results of my bullet weight experiments, which conflicted with normally accepted understandings of a homogeneous lead/tin alloy mixture, I decided to run some additional tests.

1st session:
To check the homogeneous nature of the alloy, the pot was filled with 20:1 alloy, fluxed & allowed to set for 7 hrs. Using the bottom pour feature, several bullets were cast & the lead/tin ratio measured. Then, by gently filling the ladle from the top of the alloy to minimize disturbing the alloy, several bullets were cast & the lead/tin ratio measured. The ratio of the alloy from the top of the pot was 18.5:1 and 19.5:1 from the bottom.

2nd session:
The above test was repeated after allowing the pot to set for an additional 8 hrs. The ratio of the alloy from the top & bottom of the pot was 19.5 & 19.7 respectively.

3rd session:
Finally, the test was repeated after letting the pot set overnight (approximately 12 hrs). The resulting alloy ratio from the top & bottom of the pot was 18.8 & 17.0 respectively.

The above results tend to support a homogeneous alloy versus what I measured in the earlier experiments for which I have no explanation. I’m beginning to wonder if unseen voids in the bullets affect the specific gravity (alloy ratio) measurements.

But I needed to cast up a batch of bullet for an upcoming match. So 60 bullets were cast while stirring the alloy. The result was a total weight spread of 0.8grs and the average lead/tin ratio measured at the start and finish was 20.2:1 +/- 0.2, which essentially confirmed my results from previous sessions when stirring the alloy while casting.

That’s it for me. I don’t plan on additional experiments on this subject. I’ll just be sure to stir the pot during future casting sessions. By the way, a forum member reading the results of my experiments referred me to an excellent article that was published in the Jan./Feb. 1981 issue of the Hanloader magazine. Titled, Weight Variations in Cast Bullets, it can be accessed at https://www.riflemagazine.com/magazine/P...artial.pdf

Wayne

[Lumpy Grits]

Thx Wayne
G.