A few items up from:
I use straight wheel weights.
I have a Lyman bottom-pour furnace.
The mold is a Lyman 452424FV double-cavity.
I fill the mould by placing the sprue hole tight against the pour nipple then pull away at the first sign of complete fill (a little spurt) and add a little melt to make a decent sprue lump.
I use a wooden stick to knock the sprue cutter just after the melt frosts on the sprue plate.
I dump the bullets as soon as I cut the spue.
I vary the refill time (pacing - tempo) by a count to allow the mold to cool while it is empty. I have a small (tiny) fan for cooling the mold.
I use a small loupe to visually inspect the bullets and return the culls to the melt once I've cast a fair pile (hundred or so). I have a fair cull rate, about 50% and sometimes more from this mold.
I use a commercial flux, Frankford Arsenal and flux at each add of new metal (culls or ingot).
Here are a few images of some bullets I just made and their weight distribution.
Seven bullets from the Lyman 452424FV double-cavity mold. The weight of these seven, in grains, is 253.4 (x2), 253.8 (x2), 254.2 (x2) and 254.4.
Sorry about the poor quality images, I don't have a macro setup here at home.
Now some questions.
On the sprue I notice the cut looks grainy, not a clean shiny cut. I suspect this is due to breaking the sprue off vice shearing it off but I'm not sure. What do you believe to be the cause and effect of this type sprue (as seen in the 2 magnified images)?
In order to get the bullets (mold) to fill completely I feel the melt might be pretty hot (I've ordered a thermometer). I can clearly see the milling marks transferred from the mold to the final bullets. The bullets also seem to be filled and have sharp definition at the edges. Is this a “bad” thing, high temp and high mold definition? Is this also perhaps due to my straight wheel weight alloy?
The texture of the bullets gives them a 'dull' appearance as compared to the shiny ones that have rounded edges and low mold definition. If I go a little too long and allow the mold to get hot I get frosted bullets. These frosted bullets seem to have a little less definition than the ones I retain as 'good' and have a whiteish type appearance. Are the bullets I'm calling good, the examples above, frosted?
Any help with getting me going would be appreciated.
The distribution seems good to me with the weight being near the 255 of the mold design.
Edit for spelling and clarity