runout in moulds

[pwcooley]

Yesterday while casting some .430 bullets from a new RCBS 240 grain SWC GC mould after a while I started getting some thin whisker like projections outside of the bullet cavity, at the seam of the bullet, and couldn´t get them to cast as perfect as in the beginning. First I tried tightening my grip on the mould and after this didn´t work I cleaned both inner sides of the mould but still had the same problem. It´s no big deal, I used a cutter to trim off the excess lead but it´d be nice to correct whatever is causing this. Anyone have an idea of what I´m doing wrong?

[garandsrus]

Pwcooley,

It's usually one of two things, the mold is either too hot or there is something holding the blocks apart, which could be the alignment pins.

John

[pwcooley]

Thank you John. I´ll check the pins and the corresponding holes to see if there isn´t any crud in there holding them apart.

[fourarmed]

Those whiskers are alloy that has been forced out into the vent lines. That requires pretty low surface tension in the alloy, and usually indicates that mould fillout is good. That seems at odds with your observation that fillout was not as good as earlier casts.

[runfiverun]

hold your mold up toa light and look in the middle for a seam of light.
if there is one you either got some lead in there or your pins are too far out and need to be drifted back in.
look for little bits of lead around those pins and in the alignment holes also.

[Bass Ackward]

from a new RCBS 240 grain SWC GC mould after a while I started getting some thin whisker like projections outside of the bullet cavity


The key for me here is a new mold. Very important, on new molds especially, to lubricate the pins until the mold breaks in. More important on aluminum molds because aluminum gets sticky when it get hot. This prevents pins from being pushed or pulled until they set.

[WARD O]

I ran into the same thing this past weekend. I was giving a new RCBS 44 250 K it's first try and ran into these feathers as well. They weren't there at the beginning but came later. I tried checking for any material on the mould face but didn't see anything obvious.

I had touched the pins with a stick of 'antisieze' so I expect it might be possible that some of this stuff was causing a problem with the pins. I'll have to check that.

Is it likely that the pins actually need to be driven farther into the block??

The boolits weren't frosted - isn't that usually a sign of the mould being too hot??

Ward

[GabbyM]

If you have good tin content. Like 2%. the melting point, viscosity and surface tension are all lowered. This allows you to run your melt at lower temperature and still achieve good mould fill out. With a 2/4 or 2/6 alloy you can get fins with many moulds with alloy temps over 800*. Until your mould blocks over heat you will not have frosting at those alloy temps. 750* is plenty of heat for an alloy with 1 ½ to 2% tin. I usually try to run temp at 700* or even 675* with a 2/4 alloy. Keeps the moulds cooler to increase production rate. With my Lee bottom poor the spout will freeze before the melt temperature becomes to low to fill out. With scrap WW metal I often run up around 800* + to make it work.

For the OP to have lack of good mould fill out along with finning is odd. If fillout was indeed what he ment by less perfect. Mic the bullet to see if it's over sized will tell you if the blocks are closing. That's if you've the luxury of owning a micrometer. Option would be to push one through the sizer die and view the crush. You can usually see if it was out of round or over sized. Usually when it's been working OK then won't close it's just a smear of lead on the mould faces. Take a piece of lead like a scrap bullet and rub it off like using an eraser.

[WARD O]

Question: What does 2/4 or 2/6 refer to?

Thanks for the tip on using a piece of lead to clean the mould face.

[GabbyM]

Question: What does 2/4 or 2/6 refer to?

Thanks for the tip on using a piece of lead to clean the mould face.
2/6 stands for 2% tin / 6% antimony . Which is taracorp magnum bullet alloy.
Lyman #2 is 5/5. Take WW (wheel weights) and add 1 ½ % tin and you have 2/4.
Linotype is 4/12 so you can mix it 50/50 with scrap sheet lead and maybe get a 2/6.
Ten- four their little buddy.