my bullets look OK but are dimensionally unstable, help!

[Quigley_up_Over]

I thought I was doing REALLY well with my casting, so well that I cast-up about (250) .459 x 540 grain 45001's before doing any dimensional inspection. Last night, I was really disappointed to learn that my bullet's driving band diameters vary from .459 to .454...nothing in the way of concentricity / consistency in general. I also noted a VERY heavy amount of antimonial frosting on all the bullets. I thought before since it wiped off easily it was no big deal, should I really be getting nice shiny bullets and not frosted ones?

I am melting Rotometal 1:30 alloy, using a Paul Jones 45001 mold. I run my pot on #10, which seems to give the best LOOKING bullet (minus the frosting).

I am really confused and quite honestly pretty bummed out that the pile of bullets that I thought were perfect are actually all over the place in terms of dimensional stability.

Last night, I tried turning my pot down to 6.5. The frosting subsided, but was replaced by super-dull looking bullets as opposed to nice shiny ones.

Confused. Where do I go from here? Thanks guys.

[ku4hx]

I thought I was doing REALLY well with my casting, so well that I cast-up about (250) .459 x 540 grain 45001's before doing any dimensional inspection. Last night, I was really disappointed to learn that my bullet's driving band diameters vary from .459 to .454...nothing in the way of concentricity / consistency in general. I also noted a VERY heavy amount of antimonial frosting on all the bullets. I thought before since it wiped off easily it was no big deal, should I really be getting nice shiny bullets and not frosted ones?

I am melting Rotometal 1:30 alloy, using a Paul Jones 45001 mold. I run my pot on #10, which seems to give the best LOOKING bullet (minus the frosting).

I am really confused and quite honestly pretty bummed out that the pile of bullets that I thought were perfect are actually all over the place in terms of dimensional stability.

Last night, I tried turning my pot down to 6.5. The frosting subsided, but was replaced by super-dull looking bullets as opposed to nice shiny ones.

Confused. Where do I go from here? Thanks guys.

Are you getting only a few of the improper sizes or are they just all over the place? If you're using a multi-cavity mold can you tell if any given cavity is what causing the problem? Nothing wrong with frosting per se, personally I find I get consistently better boolits if they are frosted. Holds the LLA better too. At it's most basic, sizing cast boolits makes them all uniform diameter. Have you tried sizing any?

How do they load and shoot? Can the largest be chambered? Do the smallest lead your bore? Lots of room for experimentation. This hobby is a process, not a single event, and few of us got excellent boolits in our early stages.

[41 mag fan]

Roto metals 1:30 has no antimony in it. It's a lead/tin mix.
Whats the temp you're casting at?
Are you preheating your mold before starting to cast?
Running your pot on 10 could be burning the tin out of your melt, causing the varying diameters of the drive bands.
Try running this melt around 100* over liquid state and see how it casts.
Geargnasher has stated this ideal temp of melts to be ideal. I have to agree, after experimenting.
Go and do a search on casting problems and see what you come up with, theres a wealth of knowledge in old threads on here.

[44man]

I am unclear??? Is that 1 to 30, tin, lead?
How can it get frosted?
Be aware, mold cavities get SMALLER if too hot and not all in the same direction. The high heat could be making the mold out of round.

[Junior1942]

Make sure the two mold halves are closing completely.

[mdi]

Personally, I'd run the melt and the mold cooler. The only asset of a shiny bullet over a frosted one, (in my limited experience) is eye appeal. But, shiny also indicates to me that my mold is not too hot and I get better results; less variation in diameter (this is with my iron molds, aluminum differs. My Lee molds like to be run hot).

[Quigley_up_Over]

I ran a small batch a lot colder last night. They were too hot to inspect with the calipers before I went to bed. I will inspect them after work today and report back to the forum. Thanks guys for all the help.

[MBTcustom]

Many things effect dimensional tolerance in a casting session.
These things must be controlled:
1. Mold temperature.
2. Alloy temperature.
3. Sprue cut timing.
4. The distance the silver stream has to go before entering the mold.
5. The mold must be closed completely every time.
6. I theorize that the amount of lead in the pot (if you have a bottom pour furnce) will effect the pressure of the alloy flowing out of it. (another good reason for a large pot.)
If you are truly controlling all of these variables, then I dont know what the problem is unless you have different sized cavities in that mold.

[runfiverun]

i'm gonna wait for the second report.
i'm thinking quigley might just learn something here.

[Moonie]

Do not measure with a caliper, they are not accurate enough for this measurement. Please try again with a micrometer.

[MBTcustom]

Good call Moonie, I missed that one.

[Wayne Smith]

You are using a Paul Jones mold, I'm guessing either single or double cavity. You should be able to assume that the mold is right, thus look at your casting style, tempo, and the faces of your mold. Only a little drop of lead flattened can cause the mold half's to stay open a touch and increase the diameter of your boolits.

[Sonnypie]

I ran a small batch a lot colder last night. They were too hot to inspect with the calipers before I went to bed. I will inspect them after work today and report back to the forum. Thanks guys for all the help.

I try to never go to bed when my bullets are still hot.
But then, that's just me...

[waksupi]

You may want to get a set of the Cabin Tree mold handles. They will help with consistency.

[Certaindeaf]

"10" and "6.5" might mean something but a thermometer will tell you the actual temperature.

[HangFireW8]

You are using a Paul Jones mold, I'm guessing either single or double cavity. You should be able to assume that the mold is right...

You SHOULD be able to assume, but don't. If it is a double cavity (or more), the cavities may differ. Even if it was cut right in the beginning, something may have warped, peened, or gotten out of alignment, or maybe it was never right. Even the best mold makers have a bad day.

Never assume when debugging a problem. The thing you assume may be the problem.

HF