Cast bullets drop small

[jloader]

I'm casting 38SP and 9mm.
Some of the bullets drop lower in diameter (batches, not individual bullets that are smaller).
I can feel the size diff in the sizing die - some go right thru without any effort and some take some effort to resize.

I would prefer to have them drop on the large side and resize versus having them a bit on the loose side in the cartridge. I know that I could crimp some more but they would be prone to gas-blow-by.

I suspect that I may have to better control lead temp... but not sure which way to go... I'm using Lee Production IV pot.
Have different sources of lead ingots so not sure on the exact alloy.

Would water quenching help? Seems like I've read something about that somewhere on the net... or was it just about hardness change over time.... not sure...

[Ohio3Wheels]

If you're using aluminum molds try running them hotter. Up to a point they will expand and give larger bullets. Find the temperature that gives the size you want and try to cast there.

Make smoke,

[Ranch Dog]

If you're using aluminum molds try running them hotter. Up to a point, they will expand and give larger bullets. Find the temperature that gives the size you want and try to cast there.

I agree with O3W; you probably need to cast at a bit higher temperature.

Hotter probably being the point that the slowly becoming frosted. I like working that point, the point where I get about five drops with a six-cavity mold, and then they are almost too frosted (sticking to the mold). Right here is the second good thing about an aluminum mold. You should have a damp rag on the bench that you can press the mold against to reduce the mold block heat. I end up with a rhythm where I do the five drops and cold the mold for a count of five on the rag.

Basic run of the mill air cooled alloy is perfect for the 38 Spl. The 9mm Luger; depends on what you do with it. If you want to run it at the SAAMI Max of 35.0K PS, probably going to need a tough alloy and a gas check.

[jloader]

Thank you both!
That seems to make sense...
Few casting sessions back I was starting to get frosting so I went down in temps - that could be directly corelated to size change.
I'll give that a try over the next few days...
I'm using my cast bullets for hole punching in paper so no hardened alloys or gas checks needed

[RBHarter]

Actually you'd be surprised at how hard you can push a plain based comparatively soft bullet .
Temperature will be your friend to a point and that point will depend on the mould as well as the design .

I recently found that I was running my pot way too hot , no fault of my own just a glitchy temp switch and reostat . The same setting every time apparently wasn't even close with the new pot ......
Longer bullets of the same caliber need a hotter mould not necessarily a hotter pot . I have several 45 cal moulds the 350 gr gives me 5-6 perfect drops per minute while the 250 will do 6-7 from the same pot , alloy and day . I have a 25 , 26 cal 120-140 that have to rest on the pot while I pour to keep them hot enough for good bullets but the 22 at 55 gr is happy to rest on the pot 2-3 at 10 pours/ min.
I don't think I can over run the 358-125 , 158 or RNFP nor the 401 or 452 6Cs , not with current equipment anyway . They all run fat and heavy .

You might add a little tin to the alloy also .

[horseman]

Run your melt between 700 and 725. I let the mold run hot as well, when the sprue plate becomes "to easy" to open is when I cool it with a damp sponge I keep in a small bowl with water in it. Turn the sponge every so often to keep it damp on top. Bullets will be "frosted" but the weights will run very consistent with very few culls. Just because a bullet doesn't "look good" doesn't mean it's bad as long as the base is good and it has sharp edges. Just takes a little bit of experience as to what the mold likes. I cast at a fairly quick, steady, pace.

[jloader]

I've done some 'net' reading and have run into an interesting post on LA silouhette club site at
http://www.lasc.us/castbulletnotes.htm

Here is a snip from it talking about different rate of shrinkage based on different alloy.

BulletShrinkage.JPG

So, a softer metal will have a larger shrinkage... and I did get a softer batch of metal recently...

Now I have a couple of things to play with - temp and alloy.
This will be fun...

[GasGuzzler]

I'm still not really good at it but the best thing I learned so far is shoot frosted bullets and post pics of shiny ones.

[Okie44]

I'm still not really good at it but the best thing I learned so far is shoot frosted bullets and post pics of shiny ones.

Works for me!

[jloader]

... the best thing I learned so far is shoot frosted bullets and post pics of shiny ones.

You crack me up... Guess you're right, especially that I'm not concerned with bullet fragmentation impacting paper target.