Your alloy isn't hot enough to flow into the corners before it cools.  Get the temperature up.  Thermometers aren't always accurate!  (Don't get a case of the fantods over "frosted" bullets: hotter is better if your bullets aren't filling out the mold completely.)

Also, are your pouring from a ladle or using a bottom-pour pot?  I use the latter for convenience, but generally hand-poured bullets from a ladle fill out better and are more consistent.

I use a ladle and you have to have the pot hot, the ladle hot and the mold hot and free orf oil or grease. I frequently stir the pot and flux as the impurities rise to the top and leave the ladle in the pot.. When I'm finished making a batch of bullets I leave the last ones in the mold. Don't oil the mold.

---- I have never cast a bullet, so I don't know. But I do know about solder and flux and plumbing. And if there is not enough heat the solder will look chunky and rough and dull grey when it cools.

I would imagine that if your temp gauge says it's hot enough, that it is not factoring in the amount of heat the mold will absorb.

Go hotter! - How hot is too hot? and be just under that(??)

A trick my father in law taught me was to get the mold hot as well.  And the lead above the recommended temp.

As Elitst said - don't worry about frosted - once you start let the mold cool down slightly and the frost disappears.

All good suggestions above.  Leaving the last bullets in the mold another good tip.

My father in law taught me a lot before he passed about rolling my own.  He would use a little more tin in his mixture to get harder and better forming bullets.  He also used a lyman bottom pour pot - he said the laddle was too sloppy and took too much time.  Sorry guys.

We are looking at putting his pot up for auction in a few weeks.  Trying to find the cord.

I thought the heat was also the factor but too hot does produce frosted bullets. It looks like the ideal temperature would be just under the hot frosted one. I do not mind a bit of frost on the bullets as they still seem to size fine and shoot good.

All my lead scrap is pre melted, fluxed in a cast iron pot and cast into ingots for later use. When casting the actual bullets I use a Lee bottom pour pot which works fine.

Molds are cast iron and aluminum. Obviously the cast iron takes a bit to heat up even though I pre heat them but once they are ready they cast nice.

Casting now days is limited to the larger 45 cal. bullets, 400 to 500 grains as I have boxes of the other cast bullets from years back that I probably will never shoot up. These bullets use up a lot of lead so casting is the way to go.

Will be casting some next week so I will keep an eye on the temperature and record it at what seems to be the best cast appearances.   

I have a large cast pot and propane burner. To get consistent hardness in your bullets prepare a large amount of material and mold it into ingots . I use an old muffin tin. This way you are not retesting and adjusting your hardness each pot because you did it in mass. When bullets start to frost let the mold cool for a minute and then resume your casting. If you work in a slow steady rhythm the bullets will be consistant

Thanks for reaffirming my thoughts and the great tips.

Any more ideas for casting post them here.

HG, You are correct, that is what I do to get large lots of consistent alloys. 

jessmon  - yes I melt lead into ingots and use the ingots when casting.  But, when casting I still flux and add some tin to get the lead consistency I want.

I found that the aluminum molds cool quicker than the cast iron ones and require my trying to keep them hot by placing them on the melting pot.

When using cast irons molds, I find they run hotter, I'll use 2 or 3 molds allowing for some cooling time as the bullets start to frost.

I generally will use only 2 cast iron molds for the same reason, to keep them cast in the same speed and consistency. With aluminum the same method but they do heat up quicker but also cool quicker when open.

You need to flux the casting pot even though you fluxed to ingots in the first melt as the tin still seperates and floats to the top of the pot. Fluxing will then keep the tin in the lead.

Those of you who us a thermometer what temp do you cast at? I know it varies from time to time but about 750 degrees sound right? 

Where do ya'll find the time to do this????