Half the Mould not filling out?

[August]

Why would one side of the mould continually fail to fill out properly while the opposite side of the mould is casting perfect forms???? This seems to diminish as the mould gets really hot and also if I hold the dipper in contact with the mould for a few seconds after inverting them.

I have cleaned the mould carefully and even smoked it, which helped some. Since both halves of the mould are using the same vent lines, I'm hard pressed to understand how that might be the problem, but I sure would follow any advice along that line you might have from experience.

Thanks for your help.

Oh, the Mould is a Lyman 320 grain, .378 Postel looking thing. Single cavity, of course.

[runfiverun]

venting.....

[docone31]

Still contaminated from oils. Keep on pouring untill the mold seasons.

[mooman76]

I was kind of thinking the mould is heating up unevenly. Have you tried kranking the heat up some and how long are you talking about before the other side heats up enough to get good bullets? It actually could be any of the above mentioned.

[beagle]

Okay, here's a theory and I have found it to be true but can't tell you why or how.

I bought a DC .375 meehanite mould from Walt Melander when he was running NEI. I wanted two different designs and he ran the dimensions through a computer program he had and said no, it won't work. Finally, I agreed to take it that way and use only one cavity at a time and he agreed to make it.

I got the mould and said to myself, "Walt's full of crap". I tried both cavities and Walt wasn't full of crap. One side of one cavity wouldn't fill out.

I could get fairly decent bullets until the mould got hot, then, I'd get incomplete fillout and if I persisted, the cavities would fill out but I'd get whiskers and flashing and really heavy frosting.

I asked him about it later and he said that for any given capacity of a cavity/cavities, a certain amount of block size is required to dissipate heat to allow fillout at a normal casting tempo. If the block size is too small and heat is too high, incomplete fillout is obtained.

To correct this, the temperature of the block musts be lowered and you can generally only do this by slowing down the casting tempo, placing a fan directly on the blocks or lowering the "drop distance" from the spout to the mould. Normally, lowering the casting tempo works best.

I have also encountered this phenomonen with a DC 429421 and also with nearly all of my large capacity .44 and .45 moulds. Most often I have encountered this in Lyman moulds which normally have smaller blocks than normal. Never have encountered it in aluminum moulds.

If everything else is good, slow down on how fast you cast until you get good bullets. I've even timed myself on large 545 grain .45s and that works.

No facts, no theory as to why, just my experience and what Walt told me./beagle