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greenjoytj
07-05-2012, 11:51 AM
I'm new to the bottom pour furnace method of filling the mold.
I cast some .535" round balls using a Lee double cavity mould and a new Lee Pro 4-20 bottom pour furnace.
All my cast balls look perfect but weighed a few grains less than the expected 230 grs.
I cut some of the balls in half and found a air bubble the size of a rice grain in each ball.
I was pressing the mold inlet tight against the spigot onthe bottom of the furnace.
Is the the wrong way to fill the mold with a bottom pour furnace?

bradh
07-05-2012, 12:04 PM
I hold about one inch below the spout just because I don't like a large sprue....just the way
I've always done it.

mdi
07-05-2012, 01:43 PM
I've found distance may vary from mold to spout. Different molds may like different distances from the spout. I have one mold that likes the sprue plate in contact with the spout, but most of my molds work well with 1/2"-3/4". Some molds like the pour right down the middle and some like the mold tilted or the flow just hitting the sprue hole. Boils down to what works best for you and your molds...

dragonrider
07-05-2012, 04:24 PM
1/2" to 3/4" depends on how tall the mold is. I never change the position of the mold rest.

fredj338
07-05-2012, 05:00 PM
Depends on the mold, but hand casting, I have best results "pressure" casting with the spout tight to the spru plate. For smaller bullets & HP, it gives me more uniform results.

Mk42gunner
07-05-2012, 05:14 PM
I've found distance may vary from mold to spout. Different molds may like different distances from the spout. I have one mold that likes the sprue plate in contact with the spout, but most of my molds work well with 1/2"-3/4". Some molds like the pour right down the middle and some like the mold tilted or the flow just hitting the sprue hole. Boils down to what works best for you and your molds...

This sounds like I could have written it.

Like I have said before, your molds will tell you what they want. Obviously your .535" RB does not like being held against the spout.

Weight variation can be a product of the lead alloy you use also, although it sounds like you are using pure lead.

Robert

bob208
07-05-2012, 05:22 PM
like others have said some molds like it close others farther away most rb molds like some distance. my .50-70 mold likes tobe right against the bottom.

theperfessor
07-05-2012, 06:47 PM
I've never had much luck pressure casting. Usually have 1/2" to 1" gap as others have said. Remember a round ball has the least amount of surface area for the volume it contains, and that means less heat transfer to the blocks. Couple that with Lee blocks losing heat rapidly because of their size, and the need to cast lead hotter than lead-tin-antimony alloys, and you can end up casting good looking balls with frozen air pockets in them.

Try tilting the blocks a little and let the melt swirl into the cavity. And maybe try a little hooter to let the melt stay liquid long enough for the bubbles to rise to the top.

How tight is your sprue plate? You got to let the air out when you put the metal in.

Thumbcocker
07-05-2012, 09:14 PM
I cast everything with the spout tight to the plate. I use the set screw on the valve lever to control flow rate.

williamwaco
07-05-2012, 09:38 PM
Theperfessor +1

Jack Stanley
07-05-2012, 10:04 PM
My round ball molds tend to like to be a little way from the spout and have the temperature just a bit hotter than many guys cast at .

Jack

Old Caster
07-06-2012, 10:40 PM
If you pressure pour with the spout tight to the mold, it is a good idea to slow down how fast the lead goes in. If it goes in real fast like a quarter of a second or so, it can catch dirt or air in the middle. If you slow it down so it takes about a second to a little longer air or dirt has a chance to float to the top and into the sprue. The slower you can go without causing spout freeze or constant clogging the better it works. Try different height of lead in the pot also because it can change characteristics. -- Bill --