Wierd problem with fillout

[Mk42gunner]

For the past few days I have been casting with an RCBS 32-98-SWC mold. Getting some decent boolits from it too.

The weird part is that up until yesterday, I had good fillout and perfect bases with my normal ladle pouring technique of leaving about a ½" gap between the nozzle of the RCBS ladle and the sprue plate. Today, I couldn't get a decent base to save my life until I started doing the pressure pouring method. ???

The only thing that changed is the temp is about thirty degrees (F) cooler outside today, although I am casting in a barely heated outbuilding not outside. The building has the washer and dryer in it so it has to be kept above freezing.

I guess my question is could a difference of say twenty degrees in ambient temperature cause a mold to have different filling requirements?

I haven't touched the dial on my Promelt in years, so the alloy should have been at a very similar temp. Very same alloy from the same batch. Mold was up to temp, not too cool.

Everything I can think of is the same except the ambient temp.

Got me puzzled for sure,

Robert

[Dusty Bannister]

Yes, I have had that problem in my unheated shed when casting. Usually not a great deal of trouble until the temps get down to about 40 or so for the small or short bullets. If you have very much of a draft, that is perhaps causing the issue because it is drawing the heat from the stream as it flows from the furnace. And of course the mold blocks are going to be giving off more heat in a cooler draft, if you have one. Increase the heat and cast faster and make sure you have preheated your mold well.

[DHDeal]

That could be it. I use a repurposed turkey cooker welded into a casting table and I cast under my carport. I watch the alloy temp and can keep it +/- 10°. When it's cold and I feel like casting, I have to turn up the propane some and cast faster to keep the mold happy. For me the base of the bullet tells the story on how the whole mess is doing. Matter of fact, the bases are how I cull while casting (not perfect, in the sprue pan it goes).

I know everyone does this stuff the way they do it and don't like to change up, but if I was getting good bases pressure casting, pressure casting it would be. Personally I'm pressure caster anyway so I say cast on and turn up the heat a touch. My best bullets seem to be around 800°, but it seems most cast at +/- 725° to 750°.

[Conditor22]

If the sprue plate is cold the bases won't fill out unless you pressure pour.

Do you see circles on the base of your boolits showing where the lead could as it tried to reach the edge of the boolit

I tested this by getting a cold mold and heating the sprue plate, first pour perfect bases, I'll not talk about the rest of the boolit

[country gent]

While the pot temp is probably about the same the mould blocks temp will vary with ambient temps.Speeding your cadence up may have helped some as pouring a bigger sprue on the plate. Another is the ladle and alloy in the ladle it my be cooling just enough more in the cooler building. The 1/2"open slower pour and ladle in the colder air was also dropping temps lower. The pressure pour was keeping the small stream out of the cold air and holing heat better with a faster pour.

[Bazoo]

Ambient temperature will affect not only the mould temperature but also the alloy between spout and mould.

Could be that you wernt leaving enough sprue to keep the sprue plate up to temperature too.

[beagle]

Maybe temp. Might need to up the flow a bit too. I have the same unheated building and when I start getting rounded bases, I tweak the flow a bit and it clears up. Think it might be a combination of the two problems./beagle

[jsizemore]

What the last 2 said.

[popper]

Crank up the pot temp. Heat loss is directly related to temp difference. Alloy, ladle, mould, is cooler. Unfortunately, liqiudus temp stays the same. Heat the room or alloy.

[Martin Luber]

Did your mould get contaminated with oil or the like?

[Winger Ed.]

20 degrees is a pretty big jump. I think your mold is cooling off faster than normal.
I'd up the temp in the pot a little, leave a bigger sprue puddle, and increase the pot's flow rate.

I run the temp. up until they get a little frosted, then back off the heat until they have that Chrome plated look.
Its not very scientific, but that works for me.

[Mk42gunner]

I think Dusty nailed it. I tired to post yesterday, poor internet connection wouldn't let me.

No contamination of the mold, everything was good except for the slightly rounded base. Honestly they could have probably been loaded and shot just fine after sizing.

I really believe the pot temp is fine, when I fill it the first time or two I get very frosty boolits. After that I adjust the tempo to get as Winger Ed says, "that Chrome plated look", and a very flat base.

I can hardly wait until I get my new house finished and I can cast inside again.

Thanks for the advice,

Robert

[MT Gianni]

I have cast with temps in the teens often. I need a long preheat on a hotplate, and a careful watch to let the sprue cool but not the mold.

[robg]

turn up the heat and cast quicker .in the summer i use 2 or 3 molds so i dont have to wait for the sprue to harden. when its colder i use 1 so it keeps hot