Uh oh, Houston, we have a problem.

[USSR]

Got a new 4 cavity brass mold from MP Molds, and it refuses to fill out the base. Looks like a freshly seated primer in the primer pocket looks - space around the perimeter. Sometimes there is just a little lead way down in the nose section. I've preheated the mold, the sprue plate is plenty hot, I'm at my wits end. I've got nearly a dozen of Miha's brass molds and I've never run into this. Any ideas?

Don

[skeettx]

Sounds like a tad bit of lubricant, re-clean the mold.

https://www.mp-molds.com/tipstricks/general-advice-for-using-brass-hp-hollow-point-moulds/

https://www.youtube.com/watch?v=4el8fq_YxuU

[USSR]

I've cleaned it several times, even giving the base area special attention.

Don

[tomme boy]

Pour more lead on the sprue.

[rking22]

Could be not venting at the top of the mold. Are you contact pouring, spout of ladle tight to sprue? If so try backing away and see if that helps. If so then sprue plate to mold venting is inadequate. Could be as simple as too cold metal or mold as well.

[Greg S]

Sometimes there is just a little lead way down in the nose section = mold and sprue plate are not up to temp and robbing the heat from the melt. I think you need to up the tempo and get the mold hot before starting to look at the results.

Those sprue plates on MiHec's mold are thick and need alot of heat. I pre-heat on a hot plate and just before I start casting, I flip the mold over onto the sprue plate for a few minutes. The first half dozen pours, I empty the ladle for each cavity pouring over the the sprue plate and back into the pot. Use a wooden dowel or hammer handle to cut the cold sprues. Your mold is not close to temp until your getting a 4-5 second wait for the sprue to solidify and can cut them with a gloved hand. This is typical for me after the mold is broken in.

I never try to cast with a new MiHec mold for production the first few times. I try to break one in while casting with other molds and at some point, stop with the other mold (s), put them on the hotplate to maintain temp and pull the new adopted kid off the hotplate and give it a quick spin. Once the spin is over (stop due to frustration), I open the mold and let it cool completely. Once it is cool, if I'm on a marathon session, I'll through it back on the hot plate for another go. Basically, the majority of the first two break in casting sessions come out great... after I through them back into the pot and cast in another mold that is broken in. Lol

By break in on MiHec's molds, it means 3 + heat cycles on hot plate after cleaning with soap and water then solvent on Q tips then about 3-4 short casting sessions of 10-30 pours before it starts filling out good and releasing easily. Before this, the bullets look like fudge sticks. Cast fast and run your melt hotter too. I can get away with 710-730 on a broken in mold and alittle hotter on a new mold, maybe 730-750. Once it starts casting with alittle frost around the edges you can back off the heat and slow your pace a little bit. Like I said, about the third or fourth (short) break in casting session, the mold is gonna hit it's second wind and start producing easier.

On occasions, I've opened the mold and dunked the sprue plate into the melt for a 10-15 seconds until it comes out relatively clean, wiped it off with a towel, re-lube and start pouring. If the mold and sprue are hot and you still getting incomplete bases ometimes you just need to loosen the sprue plate a little bit and if the fails, I put a small 45° bevel < .003 on the top mating edges of the blocks with a fine stone. Worst case scenario is pressure pouring. No problem for me as I ladle pour anyway.

Your not alone, hope this helps, G

AFTER THOUGHT: I think there is something to the frosting on his molds. It seems as if everything on his molds (I think 14 to date) goes better once the mold starts to frost the first time. I mean not by judicously pre-heating but by casting at a fever us rate that you gradually increase the mold temp in a controlled fashion. Once I get the initial frosted edges or a lube groove, I usually stop and cool the mold off (ambient) and the next time I use it, it finally stops fighting and starts producing. I've got two new molds and a third just finished and two more in the chute so I'm gonna do some break in speriments.

[Rattlesnake Charlie]

Clean mold and sprue plate plus keep a molten puddle in that sprue plate hole to allow for shrinkage to suck it in.

[USSR]

Could be not venting at the top of the mold.

That's my thinking as well.

Don

[USSR]

Sometimes there is just a little lead way down in the nose section = mold and sprue plate are not up to temp and robbing the heat from the melt.

Definitely not.


If the mold and sprue are hot and you still getting incomplete bases ometimes you just need to loosen the sprue plate a little bit...

Gonna try that tomorrow.

Don

[Minerat]

On my brass moulds I take a triangle ceramic stone and put a very slight 45° bevel on the top edge of both block halves. This is usually 2 to 3 strokes between each cavity and cavity to the edge of the block. This leaves a shallow "v" under the sprue plate to help in venting. You still have to pour a big puddle and properly adjust how tight it is but once you get that you get better fill out. As said above run it hot and heat cycle it at least 3 times to get the patina going. Have patience grasshopper, it will come around and when it does wow.

[gwpercle]

My Dad would tell me ...
"I see the problem...You're not holding your mouth right !"

But I'm not going to say that... Maybe the mould needs more use/heat cycling to get it seasoned aka patina built up and I would also follow Minerat's suggestion (post #10) about lightly stoning the top edges to help venting...can't hurt .
And hold your mouth differently too ...who knows the old man might have been onto something .
Gary

[USSR]

Been casting for about 10 years with brass molds, so definitely not a grasshopper.

Okay, here are the results of today's casting session. Cleaned the mold one more time, even though I knew that wasn't the problem. Preheated the mold and loosened the sprue plate bolt so that the sprue plate was loosey goosey. I then opened the sprue plate up and stuck the tip of it into the molten lead for a minute. After doing all this, fill out was much better. I then increased the temperature of my Lyman Mag 25 to 760 degrees. I've never had to cast at this high of a temperature before, but this, in addition to the other things I did was the key. Having nearly a dozen of these molds, I've come to realize that my molds are like children, each one is a little bit different. However, this mold is definitely my little red headed step-child.

Don

[DHDeal]

Don,
I have to run my alloy hotter when using my MP Molds. I try to keep it close to 750° but when pouring my first casts, I will usually let it get up to 775° (which can cause tinning on a newish mold). I only ladle cast and tend to pressure cast. Beautiful bullets when that plate gets screaming hot.

I've also modified all but my latest MP's with a screw instead of his roll pin sprue plate stop. McMaster Carr has the same screws he uses. Simple matter of pulling the roll pin and tapping the hole. I'll also drill and tap for a lock screw for this new screw. I did this so my plate can be pretty loose. A friend has a large mill so the job looks like it was done at the factory. For whatever reason, I can run my molds faster and get very very few rejects with this modification. They look like an Accurate Mold from the top and Tom's molds sure do cast easy.

[USSR]

DHDeal,

Definitely agree with you, "Tom's molds sure do cast easy". Most of my MP Molds are hollowpoint molds, and I have been running these at about 730 or 740 degrees so as to keep the pins hot. This mold being a solid mold and without pins to worry about, I figured would be a piece of cake. Wrongo! Sounds like a nice modification you did. Unfortunately, I don't a friend with a mill.

Don

[DHDeal]

I have read where you have more than a few MP's, and didn't realize this one was not a HP mold. Yeah, I would have thought a solid would be easy too.

FWIW, you really don't have to have a milling machine to do what I did. Pull the blankety blank roll pin and tap it M6 and the lock screw isn't a must have (but it helps). I wanted to do it when I got my first one, and then read about others doing it. McMaster Carr is awesome for screws and just about everything else a gearhead might want....

[Mr Peabody]

Try running the sprue plate a little bit more loose, it will vent better

[USSR]

Mr Peabody,

That's exactly what I did, in addition to other things (read post #12).

Don