Torn Boolit Bases

[Nora]

Start with the givens:
1)A torn base is caused by the sprue being cut before the lead has cooled enough. Either from impatience, the mold being to hot, or both.
2)Imperfections will cause a shot grouping to be larger than desired.
3)The larger the imperfections, the larger the group.
Ok back to the torn bases. Just how much will it effect things? Is it an aerodynamic issue with the hole in the base that is improved with a GC. A balance issue that an out of place void will cause it to wobble as would an off center hollow point? Also how much effect does it have, say at 100 yrds. fractions of an inch, or double to triple the potential shot group?

Thanks in advance

Nora

[HeavyMetal]

The condition of the boolit base is absolutely the most important part to pay attention to!

The edges should be clean and clearly defined weather it's a plain base, bevel base or gc.

Anything but perfection in this area will allow gas escape before the boolit has "squarely" exited the bore. What happens is escaping gas acts as a "steering Jet" and pushs the boolit of course. If the "crown" is not perfect you'll get the same result!

You can suffer minor imperfection in any other part of the cast boolit but not in the edge around the base!

Now let's talk about the "crater" you have in the center of your boolit base. Take a sewing needle and examine just how deep these craters are. Some/ most will stop just where you think they should visually. Others can be the tops of "voids" and can actually "swallow" the tip of a sewing needle to a considerable depth!

If your boolits pass the Needle test don't sweat it! Slow down on the next batch ( it's why I use two molds!)

If your loading a GC it will form the boolit base and this becomes a non issue. Before this bothers the boolit stability I think you'd need a crater the size of a Pea in a 44 mag boolit!

I think you'll find these shoot well if the craters are no more than "specks" on the center of the base.

Load some. shoot some, let us know how they work.

[Buckshot]

.............Heavy Metal answered the question well, so I'll just make an aadition to the original post:

1)A torn base is caused by the sprue being cut before the lead has cooled enough. Either from impatience, the mold being to hot, or both.

Lets also add in that an antimony rich alloy will also do this.

.............Buckshot

[Nora]

Thanks for the post. I don't have any problems with it myself. However I was thinking about it, and was wondering about the "what ifs" and the "how much for how much". I appreciate your input. :Fire:

This answers what I was looking for.


Now let's talk about the "crater" you have in the center of your boolit base.

If your loading a GC it will form the boolit base and this becomes a non issue. Before this bothers the boolit stability I think you'd need a crater the size of a Pea in a 44 mag boolit!

[Nora]

Lets also add in that an antimony rich alloy will also do this.

.............Buckshot

How much antimony would constitute as "rich" as compared to straight WWs? I hadn't considered this before, but defiantly a good point.

[wdr2]

For long range rifle use, a perfect flat bullet base is a must.

[HeavyMetal]

WW metal varies a lot. It's make up, I believe, is adjusted depending on the desired weight of the ww being cast at the manufacturing level.

Of course we all know that stick on ww's are much softer than the clip on ones. My idea is that it is easier to control WW's (clip on type) weight during production by altering the alloy for a given size weight.

Hope that makes sense.

So adding additional component metals, such as Antimony, allows the manufacturer to "hit" a specific , like 7/8's ounce, ww when producing them. Adding Antimony, while not as cheap as lead, doesn't require nearly as much to make a minor weight change and has the benift of making the alloy harder.

So your supply of ww alloy is going to be subject to your source of ww. If you purchased ingots you have no idea what was melted in to make them. If you purchase from a scrap yard and get to see what your buying you may have some choice in type of ww you buy. If you get them for free you get what you get, and should seperate them before smelting.

Now for the to "rich" part. All a guy at home can usually do is smelt and then cast some boolits and then look at the surface for "sign"! A very smooth surface and having to have high heat to get fillout signals mostly pure to me. I then use my hardness tester to give me a BHN number to confirm.

A very "rough" surface with a strong crystaline look to it signals Antimony content and the bigger the crystals look the higher the Antimony content. Again the hardness teaster will give you a BHN number and the higher it is the more Antimony you have in the alloy.

Of course these are boolits that are dropped from the mold into cold water which adds additional hardening and allows you to get an idea of Anitmony content.

Now it's very important to know the differernce between "frosting" and "crystaline" . Frosting has always looked ( to me) like the boolit was bead blasted and produce's a very fine "fog" effect on the surface of the alloy. The "Crystaline" effect is much courser looking.

When preparing to smelt clip on ww's I try to mix the same amount of pounds of large ( 1.5 oz or more) to little ( . 8oz or less) in the same batch. You will need to guesstimate a little because of the steel in the weights.

I then try to make as large a batch as possible, 100 lbs, and then mark it with a set of number punch's so I can keep it seperate from my other ingots. I try to make a few sample boolits during the smelting just so I can get an idea of what I wind up with and then use these "base" ingots as seeder material for specific alloys in the future.

It's to early to be this long winded but I don't know a shorter way to explain how I dertermine a "rich" Antimony content alloy.

[454PB]

You'll see those base craters with an alloy like wheelweights, but it is not caused by antimony, it's caused by a lack of tin.

If you don't think so, try casting with straight linotype. The boolits are perfect, no voids or tearing in the base, and beautifully shiney. Linotype has 12% antimony, which is 3 to 4 times the amount in wheelweight metal.......but it also has 4% tin.