Once in a while I have had moulds that don't fill completely when they're hot. Generally it is in the area where the front driving bands give way to the nose. What's happening?
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Once in a while I have had moulds that don't fill completely when they're hot. Generally it is in the area where the front driving bands give way to the nose. What's happening?
I have noticed that same phenomena, usually in a really hot mold. The boolit will be heavily frosted and other parts of the boollit will be fully filled out. I don't have a good explanation for it but I find that it goes away if I let my mold cool off a bit. In a multi cavity mold, it seems to me to be more common on the inner cavities, say the second and third on a 4 cavity.
Hopefully, one of our more scientifically inclined fellows will be able to shed some light on this.
The hotter the mold and melt, the more shrinkage involved. If the sprue puddle cools before shrinkage is finished the bullet will collapse/distorte.
Another issue may be when hot it isn't venting as good as when at temp. Some times heat causes venting to act differently.
the venting changing from the mold changing size could be the cause.
it could also be from the hot alloy concentrating heat in that area due to it hitting right there.
I'm thinking it about venting. Thanks for the ideas.
So I looked closely at the mould this morning, clean faces and vent lines. After pouring a few the problem started again, too hot. I grabbed one of my favorite single cavity moulds and put it to use at the rate of 2 singles for 1 of the double cavity. That slowed me down enough that neither get hot enough to have any problems. Seems there's limits to everything.