Getting large molds to properly fill out. Tips?

[robg]

run hot and fast,sometimes it helps to let the lead swirl into the mold rather than directly in.

[Char-Gar]

This is just not a real option for me. The larger the hole the harder it is to cut this effects wear and tear on the mold.

Use this as last resort or order new spure and drill away. I really feel collectively we have solved the probelm if you can apply our suggestions.

CW

I have opened up the spru hole on every 45 cal rifle mold I own (6 of them) with none of the effects you anticipate.

[Carrier]

So what size drill bit to enlarge the hole on a Lee mould plate? What size of hole would maximize bullet fill out?

[Hanzy4200]

Are you getting extremely frosted boolits that are wrinkly?

The extreme frosty bullets are not exhibiting the wrinkles. To those that assumed mold temp was the issue, I assure you it is not. From "warm" this thing is piping hot in 2 casts. After 5-6 I am in fear of leaving lead smears on the sprue plate as it is taking 8-9 seconds to solidify. I will fire it up again this weekend and experiment. My personal bets, after reading through your input, is likely flow speed or maybe alloy temp. My old Lee pot doesn't like being opened up on full, or she leaks like the dickens.

[Bird]

The extreme frosty bullets are not exhibiting the wrinkles. To those that assumed mold temp was the issue, I assure you it is not. From "warm" this thing is piping hot in 2 casts. After 5-6 I am in fear of leaving lead smears on the sprue plate as it is taking 8-9 seconds to solidify. I will fire it up again this weekend and experiment. My personal bets, after reading through your input, is likely flow speed or maybe alloy temp. My old Lee pot doesn't like being opened up on full, or she leaks like the dickens.

Your solution once you have reached the point of frosty bullets, is to wait a little longer between filling the mold. You should then get shiny bullets, if that is what you want. The sprue plate will run hotter than the mold, and may need a quick upside down tap on a damp rag.
My rcbs 405 grain mold does exactly the same as yours. The mold loses heat fast, a lot faster than smaller bullets, but the heat will remain in the sprue plate. Once up to temp, I time my pours, and don't have any problems except the occasional need to cool the sprue plate.

P.S set your pot temp to 780F. At lower usual temps of 720 you may never get the mold hot enough to cast decent bullets. Molds for the larger bullets don't have as much metal in them as smaller bullets, thus quicker heat loss becomes a problem, especially single cavity and aluminum molds. When you do finally get the correct mold temp, the sprue plate that gets sandwiched between lead will be too hot and cause the smearing you see.

[DonHowe]

Mold blocks with cavitiy/cavities for large bullets do hVe less mass than the same size block with cavities for small bullets but, and a very big BUT in my experience, a much larger mass of molten metal is being poured into that smaller mass. Smaller mass = quicker cooling but it also = quicker heating. Make that "less" mass of aluminum and it heat/cools even faster than iron blocks of the same physical size. I have cast with iron small cavity molds with which I struggled to cast fast enough to keep enough heat in the mold to get good bullets and 0 danger of the mold getting the mold too hot. On the other hand with those low-mass large-cavity single cavity molds which lose heat so rapidly it is no trouble at all to get them so hot as to smear molten alloy on both blocks and sprue plate. I have seen this with both iron and aluminum block molds. I have seen Lee .45-70 molds pretty quickly get so hot as to force the caster to take a break long enough for the blocks to cool.
My casting of large bullets, ie 400gr .40, .500/530gr .45, was all match quality bullets for BPCR silhouette so I was after the best bullets I could make. Production is slow enough with single cavity molds so any casting practice that forced me to stop and fix a mess or that resulted in a very high percentage of reject bullets was to be avoided. I know I am not the most proficient caster and my methods are not the only way to cast but I do know they work well.
It has been my observation that the primary consideration for many, maybe most, casters is how fast can I make them and how many in a given amount of time vs learn first to make good bullets then let speed come with practice.

[ddixie884]

Do you have a good puddle of metal on top of your sprue plate for your bullet to draw from as it cools? I had been using 4 cavity Lyman molds and bought some SAECO molds to round out my selection. I had trouble with fill and finally used a drill press and a countersink bit to open the fill holes evenly. I had a lot better performance. Charles is probably right............