MP mold 432WFN casting problem

[solman]

I starting casting again after a year and a half hiatus. I bought this mold in a group buy in 2018 and just got around to using it. I have just finished the second casting session with it and I am having a problem with boolit fillout on the base. I cast about 100 each time as it didn't seem to make sense to go further. This is a 2 cavity brass mold plain base. 432-245-250gr. I find the first cavity fills out fine but the second cavity does not leave a nice flat base. I use a Lee 4-20 bottom pour pot and pour in a continuous motion. I tried the far cavity first and then push the handle to fill the second cavity. I tried reversing this procedure filling the back cavity first and then the front. Either way the last cavity filled will be rounded base. I am using range lead that tested at 12BHN on my LBT hardness tester.
I have cast using Lee, RCBS, and Lyman molds in the past and have not run into this problem. I tried casting temp from 685-750 temp with no improvement.
I am doing something wrong? I washed the mold with dish soap and hot water before use.

[Walks]

Sprue Plate not hot enough ?

Maybe stick the striking edge of the sprue plate into the melt for 5 seconds before castiing ?

[Hickory]

Two things I'd try.
First add a little bit of tin.
Second loosen the screw on the sprue plate one half turn.
Oh, one more thing, turn the heat up a little more.

[Wheelguns 1961]

Maybe try opening up your valve so the lead comes out faster.

[Minerat]

I sometimes have to put a bevel on the sharp edges on the top of the mould where they meet. This makes a shallow "V" that lets air escape. I use a very fine ceramic stone to lightly hone the edges.

[solman]

"Second loosen the screw on the sprue plate one half turn.
Oh, one more thing, turn the heat up a little more."
Hickory you were right on this, I loosened the sprue plate a bit and turned up the heat and now it seems to be casting fine
Thanks.
Solman
Minerat how much of a bevel do put on and does the sizer clean up the base?
Just asking for my knowledge base.

[Minerat]

Just enough to take the sharp edge off each half between the cavities. I leave the edges alone in the cavities so it only lets the air out as they fill. That way I get better base fill out.

[dkf]

I break the sharp edge at the top of all my molds too. I use a super fine diamond hone, very little to just remove the sharp edge. The bevel does not show up on the bullets.

That said you likely need more heat in the mold and sprue plate. It is not uncommon for the cavity closet to the sprue plate pivot screw to be a little colder IME. I have the same mold (and over a dozen other MP brass molds, lost count exactly) and they do like to cast on the hot side. For a bottom pour pot get your flow right out of the spout and try some pressure casting too, at least until the mold is heated up good. You have to feel out the right balance of mold block temp, sprue plate temp and lead melt temp.

[solman]

Yes I see now that each mold has it's own personality and needs varying techniques. The MP mold does like to be run hotter than my other molds that was new to me as this is my first MP mold. Once I got a good rhythm going all the castings went very well.