How does alloy affect boolit size?

[GL49]

How much can you affect "as cast" boolit size by changing your alloy?

I've got a mould that casts .452-.4525 using clip-on WWs. How much effect will the addition of tin, increasing the percentage to 2%, affect the size of my boolit? Or the addition of linotype or monotype affect the size? Anyone know of where I can find information on this, or have personal experience? I'd like to be able to size to .4525 or .453, but the boolits are a little smaller than I'd like. Any ideas besides beagling the mould? I'm sizing for 45 colt and 454 Casull.

Thanks, Larry

[MT Chambers]

You should read the work by Lyman in their cast bullet handbook/s, to summarize: the harder you make your alloy the wider the bullet will drop, sometimes more then .001".

[I'll Make Mine]

Lapping the cavity is an alternate option to Beagling, and will produce a round bullet that's larger all the way around, rather than an oval. It can also get you more size increase than alloy adjustments, without changing hardness.

[cbrick]

Some info here . . .

http://www.lasc.us/CastBulletNotes.htm

In the 454 you may want/need a harder boolit but probably not in the Colt. Adding antimony will increase the diameter but also hardness and brittleness.

Rick

[Larry Gibson]

Can be as much as .001 - .002 depending on quality (% of lead, antimony, tin) in he COWWs, the temp of the mould, temp of the alloy, how quickly the alloy is poured into the cavity, etc. Most COWWs the last 20+ years have been short on tin. I arbitrarily add 2% tin as a mater of course. This blends with the antimony into the lead and makes for a better alloy.

Larry Gibson

[40Super]

I would try to spin a boolit in the cavities with some fine compound to get the mold .001-.0015 bigger rather than relying on harder alloy to get bigger. Aluminum and brass molds are pretty easy to do, just have to go slow.

[GL49]

Thanks for the replies, gentlemen.
I'm guessing a cooler alloy will cast larger boolits, assuming the alloy expands with heat, but what about the mould? Do the cavities get larger, or does the expanding metal of the mould cause them to get squeezed smaller?
Also, I've never considered the speed of the pour affecting boolit size. The mould I'm working with is a Mihec 4-cavity brass mould with a flat based boolit. To get the base of the boolit flat, I have to hold it farther away from my bottom pour Lee pot, fill it as fast as I can, trying to get the stream of lead directly in the center of the filler hole, and hold the mould perfectly level. If it's tilted or if I don't hit near the center of the hole, the base doesn't fill out around the edges. The rest of the mould is filling out fine, and it falls off the HP pins easily when I'm casting with them installed instead of the flat nose pins.
Gonna have to experiment with this one for a while. If I could gain .001, that would be great, I would settle for half that.

[cbrick]

Larry, it's possible the sprue plate isn't hot enough. MP molds have a thick steel plate and it takes a bit to get it hot enough, a large sprue puddle helps. A cool plate can do what you describe. Another possibility is the plate is not vented enough though I haven't experienced this on a Mihec mold. If getting the plate hotter doesn't work you could try very slightly chamfering the top edge of the blocks where they come together with a stone to give air a place to go. NOT a file. a file could easily take off too much material.

Rick

[GL49]

I'll try getting the sprue plate hotter, as well as adding a little tin. Stoning the edge of the blocks will be a last resort, this mould is a thing of beauty and I hate to mess with it. It started casting great right out of the box, I had no sticky cavities and never once had to tap on the mould to get the boolits to drop. I just had to learn how to get the base of the bullet square instead of looking like it had a small bevel base.
I looked closely at the lasc site, if I had scrolled down farther and finished reading, some of my questions would have been answered.

[40Super]

I have chamfered all my molds on that parting line(I have a fine file and light pressure), it has helped every one with base fillout. I do it as I'm casting, take a few swipes, then try casting some, repeat. I usually end up with about a .004-.006" chamfer, just don't get aggressive so as to go too far.
You can also try to pressure cast. It has helped with a few of my molds, but can end up with more flashing from lead being forced into any small spaces.